10 ms·

Just say No to brainteaser questions at interviews

105 points by daleroberts 14y ago

marcusf 14y ago
I'm not fond of brain teasers either, but small, self-contained questions have value. Often if they're simple enough you can use them in many interviews and establish a base line (if the candidate did a, b or c she will usually work out, if she took route d, that betrays a weakness in X etc). This is not a replacement for evaluation of a candidate on their own merits, and having a good in-depth technical conversation. But I like having something to ground my evaluations in as well and make them even slightly comparable. For reference, I do the same thing when I get interviewed; I have a few questions I ask any prospective company so I have some comparative way to evaluate them. Never bad to try to have some metrics in your process.
marcog1 14y ago
The main problem I have, is when I've seen the answer to a question but don't remember it 100%. Your brain generally goes into recall mode, and rather than actually solving the problem I sometimes give an inaccurate answer and it can become hard to kick your brain back into thinking the answer through. Sometimes telling the interviewer you've heard the question before is enough to make him move on, other times they want to hear your answer anyway.
- diminish 14y ago
  yes, one of my friends, who works aggressively on brain teasers, got accepted to a job offer due to ability to solve such questions. however he told me that he knows thousands of variations of such problems. When asked he just pretends as if he is thinking to solve them, but he said most interviewers indeed are at a beginner level for such questions.
Macsenour 14y ago
A few years ago I was interviewed by Microsoft in Salt Lake City, now closed. The job was a creative type job, a game designer. A fellow there said he was a tough interviewer. He ONLY asked me brain teaser type questions. His first question concerned a radio design 20 years from now. I drew what I thought it might look like and he seemed unimpressed with my answer. He then asked me this: "You and your family of 9 are on one side of the river, there's a flash flood coming. There is a boat but it only holds 3 people. What do you do?" I said: "I get in the bow, row to the other side, and wave 'good luck' to my family. See, I don't get along with my family very well." He got a little agitated, and told me that in this case I love my family and want to save them. He asked me to try again. I said: "I flip the boat over to make it more buoyant, put the kids on top and the adults hang on the sides." He became angry: "There are piranhas in the river so you can't tough the water. Try again." I said: "I lay the oars of the boat so that more people can ride in the boat..." He interrupted me by saying: "Just answer the question." I said: "I have given you 3 creative and interesting answers. Since you are NOT trained in psychology you don't have any way of understanding my answers you feel frustrated." He said: "This interview is over" I said: "OK, but you know nothing about me". I have refused to answer these types of questions since then.
- hrabago 14y ago
  This is one of the biggest problems with these trick questions - there really isn't a correct answer, just the answer that the interviewer wants to hear.
  - kcl 14y ago
    Kaspar Hauser, the now-educated feral child, answers the professor's questions: http://www.youtube.com/watch?v=C9uqPeIYMik http://www.youtube.com/watch?v=C9uqPeIYMik
  - deleted 14y ago
    [deleted]
- cgmorton 14y ago
  Answer: walk away from the river.
  - georgemcbay 14y ago
    Given the question at face value, this is the only answer that makes any sense. If a flash flood is coming, why would your family be any safer on one side of the river vs the other?
  - eidorianu 14y ago
    It looks like she/he was ultimately "walking away from the river" (and his family) on the first answer given.
    - Macsenour 14y ago
      True! I gave him 3 creative answers and the job required me to be creative. I felt I had shown that with my answers. In hindsight, the office was shutdown and I would have been there only a few months. The scary thought is that he's out there somewhere continuing with this interview technique.
richieb 14y ago
Here is something that I always wanted to do, but haven't had the nerve. At the end of the interview, when you are asked "Do you have any questions?", I'd like to say: "Yes. There are 5 sailors marooned on a desert island, and they collect all the coconuts (.....). So what is the number of coconuts?"
cao825 14y ago
If anyone refused to answer questions like this in an interview I was running, I would ask them to leave and tell them they wouldn't be hearing from us. I don't care what your qualifications are, if you are an asshole who will not take directions, then I don't want you in my department.
readme 14y ago
I was once asked to solve the monty hall problem a couple days after I saw the movie "21"
- aplusbi 14y ago
  Well that's okay, they did it wrong in the movie anyway (they get the constraints wrong).
- pauljburke 14y ago
  The few times I've been asked it, mentioning it by name results in them swiftly moving on ... the one time it didn't, the person didn't recognise the name and insisted I'd provided the wrong answer - which was a huge time saver for me in terms of turning them down.
  - balloot 14y ago
    Wow. They asked you the monty hall problem, AND argued that you shouldn't switch the door you picked? That's awful.
    - pauljburke 14y ago
      It's entirely possible they were trying to force me to defend the position I'd taken. It probably annoyed them that I took their pet interview question (that they expected me to struggle with) and shot it down in front of them. Not that I'm claiming any special skills - probability is a hobby of mine, this problem was a gateway drug into it and I work at the very low/noddy end of quantitative finance - so a certain familiarity with things like these is to be expected. I was more surprised the guy didn't recognise the name when I said it.
- daleroberts 14y ago
  Apparently, even Erdös did not believe the solution to that problem. Imagine saying no to him because he failed to come up with the correct solution.
willvarfar 14y ago
Crikey, you really think that attitude flies in interviews?
- mrspeaker 14y ago
  Do you mean the attitude of the post or the attitude of the headline? I don't know where the headline came from, but the original post is logical and interesting. If that didn't go down well in an interview then it certainly wouldn't be a place the poster (or I) would want to work.
  - planetguy 14y ago
    Well personally I wouldn't have minded being employee eight, or even employee eighty, at Google, and right now I'd be feeling pretty silly if I'd turned that opportunity down just because they wanted to ask me about golf balls in buses.
- jvdh 14y ago
  Unless you're young and have little to no experience, that attitude will and should fly. In that case the company should be just as much trying to convince you as you are convincing them.
  - kahawe 14y ago
    > Unless you're young and have little to no experience, that attitude will and should fly I can only see you coming across as an unpleasant person if you just start asking the interviewer how many golf balls fit into a bus right after they ask you why man hole covers are that size. And then there are companies like google (and the many who blindly copy what they know about google's process) and the few available details about their interview process all point to the fact that these brain teasers are really important to them for various reasons, so that attitude or just not answering these questions at all or asking them in return will very likely rule you out there - which is ok, of course, if you do not really care much about working for them or not. But in most companies, especially those using these dreaded brain teasers, I doubt this will "fly" and in most startups they will just talk shop with you anyway. And while these brain teasers might or might not tell them something about you, you asking the interviewer a brain teaser is most certainly not going to tell you anything about the company other than, well, they have a pretty default and quaint approach to interviews. So what remains is definitely a bad after-taste and if that is what you are going for then good for you. But don't forget, most HR drones are pitiable people who have to make impossible decisions about people they don't know based on all sorts of nonsense and lies and then they are responsible when the new hire turns out really bad... so, no wonder they rely on superstition and obscure magic to tell them the future they can't possibly know. Most importantly: If you are really that good and they all want you, you shouldn't even have to deal with HR to begin with; you should be aiming for that. So the whole thing is a completely moot point and the OP comes across as quite arrogant.
oellegaard 14y ago
This is very true. How to get past first interview, without ever knowing what you are talking about: Take 15 interviews where you fail miserably, record them all - at some point you have a pool of questions/answers that are good enough to get past the first interview.
TamDenholm 14y ago
Since i'm a contractor i get interviewed a lot, i sometimes come up against these brainteasers which i usually dont mind. Sometimes they're good questions like how would i solve problem X using X language, because thats relevant, i think its a good question. However, i hate when i get questions like "how many golf balls can you get in a double decker bus" and "whats your most embarrassing moment", both of these were questions i was actually asked in an interview. My answer to the first was "I dont know and i'm not going to try and work it out because 1) i dont have enough information and 2) its not relevant to this position. I'd happily answer hypothetical questions about situations that could plausibly come up during this position, but working out number of golf balls in a bus doesnt show you how i would solve the problem of the database running slow or validation checks not working correctly." For the second one i simply answered "I have never been embarrassed in a professional setting as i mainly just do my job and i'm not embarrassed to say 'I dont know' or to ask for help. The only times i've been embarrassed were in my personal life and those are stories not appropriate for an interview." Needless to say, these were questions asked by the CEO of a startup i thought was absolutely amazing, i had sat through a tech interview with the CTO before the CEO came in and felt i did well with the tech questions. Once the CEO came in and asked me these questions, i wondered how an awesome startup was achieving this success behind the leadership of total and utter moron. I decided not to work there as i lost all respect for the CEO.
- irahul 14y ago
  > "how many golf balls can you get in a double decker bus" > My answer to the first was "I dont know and i'm not going to try and work it out because 1) i dont have enough information and 2) its not relevant to this position. The genesis of these kind of questions is http://en.wikipedia.org/wiki/Fermi_problem http://en.wikipedia.org/wiki/Fermi_problem (checkout the classic "how many piano tuners"). Fermi approximation's purpose it to estimate without concrete data. In the end, if the numbers aren't right, you just need to replace the numbers, provided your method was correct. I am not contending its relevance(largely irrelevant). I am just pointing out the origin.
- alan_cx 14y ago
  Ah, you must be me!! I used to take this a step further. The split second one of the silly questions popped up, I'd stand up and very politely end the interview. Reactions were priceless. Interestingly, I'd often get invited back, or on a couple of occasion offered the job after a follow up phone call, where I give the sort of responses you have given. The problem I have is that these types of question suggest to me that the company doesn't really know what it wants to hire, and there for is not one I would want to work for. The problem most people have is that they really need the job and feel compelled to play along, which I can only assume these interviewers take as positive feed back.
jeffool 14y ago
Ahhh, I failed (flailed) one of these once! I spent minutes trying to figure out "You have a business card in Japanese, how do you figure out what it says?" I asked if it had the phone number, they said yes, and I said the numbers are the same as in English... They said "okay, what next?" ... I was stuck. Next? Well, I suppose I could take a photo of it and ask for someone to translate it online... Or find someone in real life to translate it for me... After a couple of minutes, they were ready to move on, disappointed, when I said "Well, short of asking for help, or Googling the phone number, I have no idea off hand how to find it." "Oh, well, searching the number, that's what we thought you were going for initially." It was. I'd thought they meant "next" as in "other than that method". Having the number was so evidently "problem solved" for me, that I didn't explicitly say "search out online". ... I suddenly felt like I was in grade school again, and my teacher had failed me for not showing the work in math class. I had the right answer, but would never get credit. I went on to flop the next question or two, as I vaguely recall.
- stephengillie 14y ago
  Sorry if it's just my tired brain not getting it. What was the solution they were looking for?
  - jeffool 14y ago
    Edited for clarity, sorry. I didn't explicitly say "okay, then I call the number," or "search it online". As far as they were concerned I stopped at "okay. I found a phone number... Then I take a picture of it." It boils down to me not being perfectly clear, I guess. No hard feelings or anything, of course. Like I said, I threw myself off my game anyway.
    - deleted 14y ago
      [deleted]
- ww520 14y ago
  Why is the answer of asking a friend not acceptable? Since it's an open ended question, any reasonably open ended answer would do.
kator 14y ago
From the article: "I'm going to ask you to solve one of my problems for every problem you ask me. Remember, an interview is a two-way process, I'm trying to determine if I want to work with you too." This is the best part really.. Instead of "just say no" remember it's a dialog. If the brainteaser is interesting or you can quickly respond to how you would approach solving it then don't be an jerk about it. And feel free to have a dialog ask something back and see how they approach problem solving etc. Make it fun and interesting for all involved. If you're going to work with these people you might as well start right now in the interview! I never take an interview with a potential client or employer without having a very clear set of my own questions for them and getting those answered. I often ask off the wall questions or talk about a deep problem we solved recently and ask for the candidate for ideas on how they would approach the problem. I always share the answer we came up with. The reason for the question is not a perfect answer but to see how a candidate approaches potentially solving the question.
maeon3 14y ago
"How much would you charge to naturally irrigate the sahara desert"? "How many golf balls can you fit in a bus" "How many piano tuners could be employed in Seattle? These questions do have everything to do with a programming job, it tests your ability to take an abstract problem and break it down logically into reasonable parts. It's called a Fermi problem and if you are incapable of thinking through them, I don't want to work with you. http://en.wikipedia.org/wiki/Fermi_problem http://en.wikipedia.org/wiki/Fermi_problem
- richieb 14y ago
  Really?! Is this why estimates for software cost and development time sooooo on the money?
- chc 14y ago
  You're really saying you don't want to work with people who: 1. Don't know the volume of a golf ball 2. Don't know the volume of a bus 3. Don't know the amount of a bus's volume taken up by seats and other protrusions I think that's a little silly. I strongly doubt a single one of those will make you a better programmer. Likewise, problem 1 is a physics problem. If you're applying for a job programming physics simulations or video game engines, it could be relevant, but otherwise I don't see how knowing the physics of water would be helpful in the day-to-day experience of programming. I see how the underlying skills of solving the problems could be helpful, but in practice it seems like brainteasers tend to be more trivia than problem-solving.
  - maeon3 14y ago
    You are not tested on your ability to remember the golf ball diameter or equation to calculate how many spheres of diameter d can fit in cube c. You are expected to demonstrate you can roll the concept around in your mind and make progress toward answering the problem. When you do interviews you'll find people who literally can't think to save their own lives. Their minds have atrophied to the point that the only way they can solve a problem is to have their hands held by a competent person and told "now i need you to find the volume of a gold ball", at which point they would have to be instructed how to do even that. There are some idiots out there who have brains that have gone into coasting mode. No new learning, no new problems, everything they learned up till this point is the only thing they are capable of. You want to weed these people out quick. This question does that wonderfully. The incorrect answer is "ummm. I donno, and i don't know how to start.... Hold me".
EnderMB 14y ago
Not everyone who asks these problems is an idiot. Given the amount of dick-swinging that goes on from Google employees and the famed interviews one gets from the big tech companies I can imagine a lot of younger managers reading these and thinking that it's how you get hold of great engineers. The simple fact is that a lot of the time interviewers aren't experienced at interviewing, and most of them will spend longer formulating a process than an interviewee will spend preparing for said interview. Anyway, surely the ideal thing to do would be to play along with the interview, answer the stupid question as best as you can and when the interviewer ends with "any questions for us?" you ask them why the felt it was necessary to test you on a general-purpose brainteaser with no relevance to the job when they could have asked something more relevant, like "x". This way you show that you roughly know what you're doing, you're aware of how the interview went and you've provided a question that will make people sit up and think.
jonnathanson 14y ago
I'm going to take the contrarian point of view here: partially for the sport of it, and partially because I genuinely think there's value in puzzles and brainteasers -- though I do think the value is limited, circumstantial, and merely one datum out of many in an interview. These questions are about having a logical process, regardless of where it gets you, and spelling that process out in a sequential fashion. It's more important to communicate "I do X, and check for Y. Then I do Y, and check for Z" than it is to arrive at a reasonably accurate Z. The added component of pressure (i.e., you've only got a few minutes, in the uncomfortable setting of an interview, in which to answer the question) helps (or allegedly helps) detect your ability to remain calm and logical under tight deadlines. Basically, the question is asking "Under pressure, and faced with a seemingly insurmountable problem, will this candidate give up, or will he try to address obstacles in a rational, collected, and systemized fashion?" They're essentially variants on the Kobayashi-Maru test of Star Trek fame. Furthermore, I don't agree with the apparent consensus that oddball "puzzle" questions would be better replaced with more technically relevant brainteasers. That's not the point. You have technical questions to test your technical literacy. These questions are trying to test your character. (Brainteasers are often non-technical precisely because the interviewer doesn't want you to be able to fall back on existing knowledge as an escape hatch from the question). Some brainteaser/puzzle questions are much more inane than others, but the exercise itself isn't entirely worthless. I have never asked a puzzle question in an interview. If I were compelled to do so, I would never hire someone purely on the basis of his or her performance on one. It's one of the least important variables in a hiring process. But I'd consider with some skepticism anyone who outright refuses to answer a brainteaser, or who gets totally flummoxed by one, or who gives up without at least attempting to work out an approach. Ultimately, no single type of interview question is flawless. That's why you have a wide variety in your arsenal. You've got technical questions, case questions, puzzle questions, whiteboard questions, and even the oft-derided "Tell me about a time when..." questions. In isolation, none of these types is sufficient. In combination, they test different aspects of a candidate's thought process and preparation.
- daleroberts 14y ago
  Brainteasers and problems are fun and I love doing them. I just think it's not appropriate for an interview, especially when you catch an interviewer presenting you with questions that are simply taken from known 'problem banks'. I could have easily pretended to work through them like I've never seen them before but I think it's a lot more truthful to call them out and say 'I know all your questions'.
patio11 14y ago
Just say no to interviews. (Seriously. If a decision maker wants you hired nothing resembling one takes place.)
- balloot 14y ago
  That is just plain stupid. I wouldn't want to work anywhere that would hire me, or anyone else on my team, without a proper interview.
- memset 14y ago
  I realize (presume?) that what you are saying is meant to be a bit of hyperbole, but most of us are not (yet!) so well-connected that a decision-maker would offer a job without this kind of screening process.
  - wglb 14y ago
    I don't think so. Last four gigs I had involved nothing even remotely resembling an interview.
- kstenerud 14y ago
  Yeah, and this is how the boss's nephew gets hired into a management position he's unqualified for, poisons the culture, destroys morale, and causes a mass-exodus of quality people. I wouldn't even hire my best friend without him interviewing with 4 people (individually) who would be working with or close to him. I also wouldn't take part in the interview myself, to ensure that the treatment was 100% fair and merit based. A personal recommendation gets you in the door to the interview faster, but you still have to prove yourself, and if you're really that good you'd want us to prove ourselves as well before signing on.
  - chc 14y ago
    That's probably also how Yukihiro Matsumoto, the creator of Ruby, got hired by Heroku. Sometimes an interview really isn't necessary and can only do harm.
sambeau 14y ago
The most important point in this post is this: "an interview is a two-way process". I am constantly surprised how many people come out of interviews without asking detailed questions about the company, job, culture and work atmosphere. You have to be more sure that that they will be a good fit for you than you have to be for them. You will be one of many: they will be everything to you, probably for years.
- GoodIntentions 14y ago
  This is so completely true. The company is being assessed as much as the candidate. Probably anyone who has interviewed candidates has lost one that they really wanted to hire simply because the company 'failed the interview'. I know I have. Worthwhile candidates tend to have criteria and the self esteem required to ask questions right back at you.
tokenadult 14y ago
The review article "The Validity and Utility of Selection Models in Personnel Psychology: Practical and Theoretical Implications of 85 Years of Research Findings" http://mavweb.mnsu.edu/howard/Schmidt%20and%20Hunter%201998%20Validity%20and%20Utility%20Psychological%20Bulletin.pdf http://mavweb.mnsu.edu/howard/Schmidt%20and%20Hunter%201998%... sums up, current to 1998, much of the HUGE peer-reviewed professional literature on the industrial and organizational psychology devoted to business hiring practices. There are many kinds of hiring screens, such as resume reviews for job experience, telephone interviews, in-person interviews, checks for academic credentials, and so on. There is much published study research on how job applicants perform after they are hired in a wide variety of occupations. The overall summary of the industrial psychology research in reliable secondary sources is that two kinds of job screening procedures work reasonably well (but only about at the 0.5 level, standing alone). One is a general cognitive ability test (an IQ-like test, such as the Wonderlic personnel screening test). Another is a work-sample test, where the applicant does an actual task or group of tasks like what the applicant will do on the job if hired. Each of these kinds of tests has about the same validity in screening applicants for jobs, with the general cognitive ability test better predicting success for applicants who will be trained into a new job. Neither is perfect (both operate at about 0.5 level in validation studies), but both are better than anything else that has been tested in rigorous research, across a wide variety of occupations. So if you are hiring for your company, it's a good idea to think about how to build a work-sample test into all of your hiring processes. For legal reasons in the United States (the same consideration does not apply in other countries), it is difficult to give job applicants a straight-up IQ test (as was commonplace in my parents' generation) as a routine part of a hiring process. The Griggs v. Duke Power, 401 U.S. 424 (1971) case in the United States Supreme Court http://scholar.google.com/scholar_case?case=8655598674229196978&q=Griggs+Duke+Power&hl=en&as_sdt=2,24 http://scholar.google.com/scholar_case?case=8655598674229196... held that cognitive ability tests used in hiring that could have a "disparate impact" on applicants of some protected classes must "bear a demonstrable relationship to successful performance of the jobs for which it was used." In other words, a company that wants to use a test like the Wonderlic, or like the SAT, or like the current WAIS or Stanford-Binet IQ tests, in a hiring process had best conduct a specific validation study of the test related to performance on the job in question. Some companies do the validation study, and use IQ-like tests in hiring. Other companies use IQ-like tests in hiring and hope that no one sues (which is not what I would advise any company). Note that a brain-teaser-type test used in a hiring process might be illegal if it can be shown to have disparate impact on some job applicants and is not supported by a validation study demonstrating that the test is related to successful performance on the job. Companies outside the United States are regulated by different laws.
b0sk 14y ago
A contrarian p.o.v: They are going to lose out on exceptional cases where the candidate is a great engineer but is not able to devise a strategy towards a solution. However, there is a huge correlation between a good engineer and the ability to arrive at the solution (keep in mind they look at how you arrive at the solution too) Personally, I'd make the candidate solve a decent intermediate level problem using a computer (and Google too). Give him/her the closest approximation of the typical job environment.
mgkimsal 14y ago
I've had a few of these in my time, and I think, to an extent, they're legit, and I'll explain why. I was asked once - "how many gas pumps are in Raleigh?". I asked back "do you mean pumps for the general public, or do we need to include commercial/industrial pumps too?" and "do you actually mean Raleigh proper or the metro Raleigh area? if so, how do we define that? All of the county?" Next question was "go to the whiteboard and design a house". I took out the marker, started to draw, then turned and asked "who will be living there? Is this a single family or duplex? mobile home? stick built or modular?" and a couple other questions. I was told I was the first people to ask questions before drawing. I take the point of the brainteaser-type questions to be "how do you react to issues that come up where you don't know a lot of stuff?". For some positions, this is less important, but if you're a customer-facing position - even in development, you may interact with customers or other business units - how do you react when you get odd-ball "left field"-type questions? Do you keep your cool? Do you just react and say "that's stupid!"? Do you walk out in protest? Do you probe for more detailed information before making a pronouncement? More than ever, I think 'brainteaser' questions are far more about personality-judging than intellect or even raw "problem solving" ability.
- msprague 14y ago
  Yeah, I agree with this. I've been asked a similar problem to the gas pump one and a brain teaser one as well. The goal for them is to be able to get a better feel for how you deal with the problems, not necessarily the solutions that you come up and how accurate they are. Being a dick to an interviewer (as basically suggested in comments above) is great if you like being unemployed.
  - mgkimsal 14y ago
    Additionally, though (and I think you're saying this), it's not just how you come up with a solution from a technical/procedural standpoint. It's more - how do you react in situations that are outside of your comfortzone? And as you said, being rude to an interviewer is a sure way to stay outside their company.

105 points by daleroberts 14y ago

I'm not fond of brain teasers either, but small, self-contained questions have value. Often if they're simple enough you can use them in many interviews and establish a base line (if the candidate did a, b or c she will usually work out, if she took route d, that betrays a weakness in X etc). This is not a replacement for evaluation of a candidate on their own merits, and having a good in-depth technical conversation. But I like having something to ground my evaluations in as well and make them even slightly comparable. For reference, I do the same thing when I get interviewed; I have a few questions I ask any prospective company so I have some comparative way to evaluate them. Never bad to try to have some metrics in your process.

marcog1 14y ago

The main problem I have, is when I've seen the answer to a question but don't remember it 100%. Your brain generally goes into recall mode, and rather than actually solving the problem I sometimes give an inaccurate answer and it can become hard to kick your brain back into thinking the answer through. Sometimes telling the interviewer you've heard the question before is enough to make him move on, other times they want to hear your answer anyway.

diminish 14y ago
yes, one of my friends, who works aggressively on brain teasers, got accepted to a job offer due to ability to solve such questions. however he told me that he knows thousands of variations of such problems. When asked he just pretends as if he is thinking to solve them, but he said most interviewers indeed are at a beginner level for such questions.

Macsenour 14y ago

A few years ago I was interviewed by Microsoft in Salt Lake City, now closed. The job was a creative type job, a game designer. A fellow there said he was a tough interviewer. He ONLY asked me brain teaser type questions. His first question concerned a radio design 20 years from now. I drew what I thought it might look like and he seemed unimpressed with my answer. He then asked me this: "You and your family of 9 are on one side of the river, there's a flash flood coming. There is a boat but it only holds 3 people. What do you do?" I said: "I get in the bow, row to the other side, and wave 'good luck' to my family. See, I don't get along with my family very well." He got a little agitated, and told me that in this case I love my family and want to save them. He asked me to try again. I said: "I flip the boat over to make it more buoyant, put the kids on top and the adults hang on the sides." He became angry: "There are piranhas in the river so you can't tough the water. Try again." I said: "I lay the oars of the boat so that more people can ride in the boat..." He interrupted me by saying: "Just answer the question." I said: "I have given you 3 creative and interesting answers. Since you are NOT trained in psychology you don't have any way of understanding my answers you feel frustrated." He said: "This interview is over" I said: "OK, but you know nothing about me". I have refused to answer these types of questions since then.

hrabago 14y ago
This is one of the biggest problems with these trick questions - there really isn't a correct answer, just the answer that the interviewer wants to hear.
- kcl 14y ago
  Kaspar Hauser, the now-educated feral child, answers the professor's questions: http://www.youtube.com/watch?v=C9uqPeIYMik http://www.youtube.com/watch?v=C9uqPeIYMik
- deleted 14y ago
  [deleted]
cgmorton 14y ago
Answer: walk away from the river.
- georgemcbay 14y ago
  Given the question at face value, this is the only answer that makes any sense. If a flash flood is coming, why would your family be any safer on one side of the river vs the other?
- eidorianu 14y ago
  It looks like she/he was ultimately "walking away from the river" (and his family) on the first answer given.
  - Macsenour 14y ago
    True! I gave him 3 creative answers and the job required me to be creative. I felt I had shown that with my answers. In hindsight, the office was shutdown and I would have been there only a few months. The scary thought is that he's out there somewhere continuing with this interview technique.

richieb 14y ago

Here is something that I always wanted to do, but haven't had the nerve. At the end of the interview, when you are asked "Do you have any questions?", I'd like to say: "Yes. There are 5 sailors marooned on a desert island, and they collect all the coconuts (.....). So what is the number of coconuts?"

cao825 14y ago

If anyone refused to answer questions like this in an interview I was running, I would ask them to leave and tell them they wouldn't be hearing from us. I don't care what your qualifications are, if you are an asshole who will not take directions, then I don't want you in my department.

readme 14y ago

I was once asked to solve the monty hall problem a couple days after I saw the movie "21"

aplusbi 14y ago
Well that's okay, they did it wrong in the movie anyway (they get the constraints wrong).
pauljburke 14y ago
The few times I've been asked it, mentioning it by name results in them swiftly moving on ... the one time it didn't, the person didn't recognise the name and insisted I'd provided the wrong answer - which was a huge time saver for me in terms of turning them down.
- balloot 14y ago
  Wow. They asked you the monty hall problem, AND argued that you shouldn't switch the door you picked? That's awful.
  - pauljburke 14y ago
    It's entirely possible they were trying to force me to defend the position I'd taken. It probably annoyed them that I took their pet interview question (that they expected me to struggle with) and shot it down in front of them. Not that I'm claiming any special skills - probability is a hobby of mine, this problem was a gateway drug into it and I work at the very low/noddy end of quantitative finance - so a certain familiarity with things like these is to be expected. I was more surprised the guy didn't recognise the name when I said it.
daleroberts 14y ago
Apparently, even Erdös did not believe the solution to that problem. Imagine saying no to him because he failed to come up with the correct solution.

willvarfar 14y ago

Crikey, you really think that attitude flies in interviews?

mrspeaker 14y ago
Do you mean the attitude of the post or the attitude of the headline? I don't know where the headline came from, but the original post is logical and interesting. If that didn't go down well in an interview then it certainly wouldn't be a place the poster (or I) would want to work.
- planetguy 14y ago
  Well personally I wouldn't have minded being employee eight, or even employee eighty, at Google, and right now I'd be feeling pretty silly if I'd turned that opportunity down just because they wanted to ask me about golf balls in buses.
jvdh 14y ago
Unless you're young and have little to no experience, that attitude will and should fly. In that case the company should be just as much trying to convince you as you are convincing them.
- kahawe 14y ago
  > Unless you're young and have little to no experience, that attitude will and should fly I can only see you coming across as an unpleasant person if you just start asking the interviewer how many golf balls fit into a bus right after they ask you why man hole covers are that size. And then there are companies like google (and the many who blindly copy what they know about google's process) and the few available details about their interview process all point to the fact that these brain teasers are really important to them for various reasons, so that attitude or just not answering these questions at all or asking them in return will very likely rule you out there - which is ok, of course, if you do not really care much about working for them or not. But in most companies, especially those using these dreaded brain teasers, I doubt this will "fly" and in most startups they will just talk shop with you anyway. And while these brain teasers might or might not tell them something about you, you asking the interviewer a brain teaser is most certainly not going to tell you anything about the company other than, well, they have a pretty default and quaint approach to interviews. So what remains is definitely a bad after-taste and if that is what you are going for then good for you. But don't forget, most HR drones are pitiable people who have to make impossible decisions about people they don't know based on all sorts of nonsense and lies and then they are responsible when the new hire turns out really bad... so, no wonder they rely on superstition and obscure magic to tell them the future they can't possibly know. Most importantly: If you are really that good and they all want you, you shouldn't even have to deal with HR to begin with; you should be aiming for that. So the whole thing is a completely moot point and the OP comes across as quite arrogant.

oellegaard 14y ago

This is very true. How to get past first interview, without ever knowing what you are talking about: Take 15 interviews where you fail miserably, record them all - at some point you have a pool of questions/answers that are good enough to get past the first interview.

TamDenholm 14y ago

Since i'm a contractor i get interviewed a lot, i sometimes come up against these brainteasers which i usually dont mind. Sometimes they're good questions like how would i solve problem X using X language, because thats relevant, i think its a good question. However, i hate when i get questions like "how many golf balls can you get in a double decker bus" and "whats your most embarrassing moment", both of these were questions i was actually asked in an interview. My answer to the first was "I dont know and i'm not going to try and work it out because 1) i dont have enough information and 2) its not relevant to this position. I'd happily answer hypothetical questions about situations that could plausibly come up during this position, but working out number of golf balls in a bus doesnt show you how i would solve the problem of the database running slow or validation checks not working correctly." For the second one i simply answered "I have never been embarrassed in a professional setting as i mainly just do my job and i'm not embarrassed to say 'I dont know' or to ask for help. The only times i've been embarrassed were in my personal life and those are stories not appropriate for an interview." Needless to say, these were questions asked by the CEO of a startup i thought was absolutely amazing, i had sat through a tech interview with the CTO before the CEO came in and felt i did well with the tech questions. Once the CEO came in and asked me these questions, i wondered how an awesome startup was achieving this success behind the leadership of total and utter moron. I decided not to work there as i lost all respect for the CEO.

irahul 14y ago
> "how many golf balls can you get in a double decker bus" > My answer to the first was "I dont know and i'm not going to try and work it out because 1) i dont have enough information and 2) its not relevant to this position. The genesis of these kind of questions is http://en.wikipedia.org/wiki/Fermi_problem http://en.wikipedia.org/wiki/Fermi_problem (checkout the classic "how many piano tuners"). Fermi approximation's purpose it to estimate without concrete data. In the end, if the numbers aren't right, you just need to replace the numbers, provided your method was correct. I am not contending its relevance(largely irrelevant). I am just pointing out the origin.
alan_cx 14y ago
Ah, you must be me!! I used to take this a step further. The split second one of the silly questions popped up, I'd stand up and very politely end the interview. Reactions were priceless. Interestingly, I'd often get invited back, or on a couple of occasion offered the job after a follow up phone call, where I give the sort of responses you have given. The problem I have is that these types of question suggest to me that the company doesn't really know what it wants to hire, and there for is not one I would want to work for. The problem most people have is that they really need the job and feel compelled to play along, which I can only assume these interviewers take as positive feed back.

jeffool 14y ago

Ahhh, I failed (flailed) one of these once! I spent minutes trying to figure out "You have a business card in Japanese, how do you figure out what it says?" I asked if it had the phone number, they said yes, and I said the numbers are the same as in English... They said "okay, what next?" ... I was stuck. Next? Well, I suppose I could take a photo of it and ask for someone to translate it online... Or find someone in real life to translate it for me... After a couple of minutes, they were ready to move on, disappointed, when I said "Well, short of asking for help, or Googling the phone number, I have no idea off hand how to find it." "Oh, well, searching the number, that's what we thought you were going for initially." It was. I'd thought they meant "next" as in "other than that method". Having the number was so evidently "problem solved" for me, that I didn't explicitly say "search out online". ... I suddenly felt like I was in grade school again, and my teacher had failed me for not showing the work in math class. I had the right answer, but would never get credit. I went on to flop the next question or two, as I vaguely recall.

stephengillie 14y ago
Sorry if it's just my tired brain not getting it. What was the solution they were looking for?
- jeffool 14y ago
  Edited for clarity, sorry. I didn't explicitly say "okay, then I call the number," or "search it online". As far as they were concerned I stopped at "okay. I found a phone number... Then I take a picture of it." It boils down to me not being perfectly clear, I guess. No hard feelings or anything, of course. Like I said, I threw myself off my game anyway.
  - deleted 14y ago
    [deleted]
ww520 14y ago
Why is the answer of asking a friend not acceptable? Since it's an open ended question, any reasonably open ended answer would do.

kator 14y ago

From the article: "I'm going to ask you to solve one of my problems for every problem you ask me. Remember, an interview is a two-way process, I'm trying to determine if I want to work with you too." This is the best part really.. Instead of "just say no" remember it's a dialog. If the brainteaser is interesting or you can quickly respond to how you would approach solving it then don't be an jerk about it. And feel free to have a dialog ask something back and see how they approach problem solving etc. Make it fun and interesting for all involved. If you're going to work with these people you might as well start right now in the interview! I never take an interview with a potential client or employer without having a very clear set of my own questions for them and getting those answered. I often ask off the wall questions or talk about a deep problem we solved recently and ask for the candidate for ideas on how they would approach the problem. I always share the answer we came up with. The reason for the question is not a perfect answer but to see how a candidate approaches potentially solving the question.

maeon3 14y ago

"How much would you charge to naturally irrigate the sahara desert"? "How many golf balls can you fit in a bus" "How many piano tuners could be employed in Seattle? These questions do have everything to do with a programming job, it tests your ability to take an abstract problem and break it down logically into reasonable parts. It's called a Fermi problem and if you are incapable of thinking through them, I don't want to work with you. http://en.wikipedia.org/wiki/Fermi_problem http://en.wikipedia.org/wiki/Fermi_problem

richieb 14y ago
Really?! Is this why estimates for software cost and development time sooooo on the money?
chc 14y ago
You're really saying you don't want to work with people who: 1. Don't know the volume of a golf ball 2. Don't know the volume of a bus 3. Don't know the amount of a bus's volume taken up by seats and other protrusions I think that's a little silly. I strongly doubt a single one of those will make you a better programmer. Likewise, problem 1 is a physics problem. If you're applying for a job programming physics simulations or video game engines, it could be relevant, but otherwise I don't see how knowing the physics of water would be helpful in the day-to-day experience of programming. I see how the underlying skills of solving the problems could be helpful, but in practice it seems like brainteasers tend to be more trivia than problem-solving.
- maeon3 14y ago
  You are not tested on your ability to remember the golf ball diameter or equation to calculate how many spheres of diameter d can fit in cube c. You are expected to demonstrate you can roll the concept around in your mind and make progress toward answering the problem. When you do interviews you'll find people who literally can't think to save their own lives. Their minds have atrophied to the point that the only way they can solve a problem is to have their hands held by a competent person and told "now i need you to find the volume of a gold ball", at which point they would have to be instructed how to do even that. There are some idiots out there who have brains that have gone into coasting mode. No new learning, no new problems, everything they learned up till this point is the only thing they are capable of. You want to weed these people out quick. This question does that wonderfully. The incorrect answer is "ummm. I donno, and i don't know how to start.... Hold me".

EnderMB 14y ago

Not everyone who asks these problems is an idiot. Given the amount of dick-swinging that goes on from Google employees and the famed interviews one gets from the big tech companies I can imagine a lot of younger managers reading these and thinking that it's how you get hold of great engineers. The simple fact is that a lot of the time interviewers aren't experienced at interviewing, and most of them will spend longer formulating a process than an interviewee will spend preparing for said interview. Anyway, surely the ideal thing to do would be to play along with the interview, answer the stupid question as best as you can and when the interviewer ends with "any questions for us?" you ask them why the felt it was necessary to test you on a general-purpose brainteaser with no relevance to the job when they could have asked something more relevant, like "x". This way you show that you roughly know what you're doing, you're aware of how the interview went and you've provided a question that will make people sit up and think.

jonnathanson 14y ago

I'm going to take the contrarian point of view here: partially for the sport of it, and partially because I genuinely think there's value in puzzles and brainteasers -- though I do think the value is limited, circumstantial, and merely one datum out of many in an interview. These questions are about having a logical process, regardless of where it gets you, and spelling that process out in a sequential fashion. It's more important to communicate "I do X, and check for Y. Then I do Y, and check for Z" than it is to arrive at a reasonably accurate Z. The added component of pressure (i.e., you've only got a few minutes, in the uncomfortable setting of an interview, in which to answer the question) helps (or allegedly helps) detect your ability to remain calm and logical under tight deadlines. Basically, the question is asking "Under pressure, and faced with a seemingly insurmountable problem, will this candidate give up, or will he try to address obstacles in a rational, collected, and systemized fashion?" They're essentially variants on the Kobayashi-Maru test of Star Trek fame. Furthermore, I don't agree with the apparent consensus that oddball "puzzle" questions would be better replaced with more technically relevant brainteasers. That's not the point. You have technical questions to test your technical literacy. These questions are trying to test your character. (Brainteasers are often non-technical precisely because the interviewer doesn't want you to be able to fall back on existing knowledge as an escape hatch from the question). Some brainteaser/puzzle questions are much more inane than others, but the exercise itself isn't entirely worthless. I have never asked a puzzle question in an interview. If I were compelled to do so, I would never hire someone purely on the basis of his or her performance on one. It's one of the least important variables in a hiring process. But I'd consider with some skepticism anyone who outright refuses to answer a brainteaser, or who gets totally flummoxed by one, or who gives up without at least attempting to work out an approach. Ultimately, no single type of interview question is flawless. That's why you have a wide variety in your arsenal. You've got technical questions, case questions, puzzle questions, whiteboard questions, and even the oft-derided "Tell me about a time when..." questions. In isolation, none of these types is sufficient. In combination, they test different aspects of a candidate's thought process and preparation.

daleroberts 14y ago
Brainteasers and problems are fun and I love doing them. I just think it's not appropriate for an interview, especially when you catch an interviewer presenting you with questions that are simply taken from known 'problem banks'. I could have easily pretended to work through them like I've never seen them before but I think it's a lot more truthful to call them out and say 'I know all your questions'.

patio11 14y ago

Just say no to interviews. (Seriously. If a decision maker wants you hired nothing resembling one takes place.)

balloot 14y ago
That is just plain stupid. I wouldn't want to work anywhere that would hire me, or anyone else on my team, without a proper interview.
memset 14y ago
I realize (presume?) that what you are saying is meant to be a bit of hyperbole, but most of us are not (yet!) so well-connected that a decision-maker would offer a job without this kind of screening process.
- wglb 14y ago
  I don't think so. Last four gigs I had involved nothing even remotely resembling an interview.
kstenerud 14y ago
Yeah, and this is how the boss's nephew gets hired into a management position he's unqualified for, poisons the culture, destroys morale, and causes a mass-exodus of quality people. I wouldn't even hire my best friend without him interviewing with 4 people (individually) who would be working with or close to him. I also wouldn't take part in the interview myself, to ensure that the treatment was 100% fair and merit based. A personal recommendation gets you in the door to the interview faster, but you still have to prove yourself, and if you're really that good you'd want us to prove ourselves as well before signing on.
- chc 14y ago
  That's probably also how Yukihiro Matsumoto, the creator of Ruby, got hired by Heroku. Sometimes an interview really isn't necessary and can only do harm.

sambeau 14y ago

The most important point in this post is this: "an interview is a two-way process". I am constantly surprised how many people come out of interviews without asking detailed questions about the company, job, culture and work atmosphere. You have to be more sure that that they will be a good fit for you than you have to be for them. You will be one of many: they will be everything to you, probably for years.

GoodIntentions 14y ago
This is so completely true. The company is being assessed as much as the candidate. Probably anyone who has interviewed candidates has lost one that they really wanted to hire simply because the company 'failed the interview'. I know I have. Worthwhile candidates tend to have criteria and the self esteem required to ask questions right back at you.

tokenadult 14y ago

The review article "The Validity and Utility of Selection Models in Personnel Psychology: Practical and Theoretical Implications of 85 Years of Research Findings" http://mavweb.mnsu.edu/howard/Schmidt%20and%20Hunter%201998%20Validity%20and%20Utility%20Psychological%20Bulletin.pdf http://mavweb.mnsu.edu/howard/Schmidt%20and%20Hunter%201998%... sums up, current to 1998, much of the HUGE peer-reviewed professional literature on the industrial and organizational psychology devoted to business hiring practices. There are many kinds of hiring screens, such as resume reviews for job experience, telephone interviews, in-person interviews, checks for academic credentials, and so on. There is much published study research on how job applicants perform after they are hired in a wide variety of occupations. The overall summary of the industrial psychology research in reliable secondary sources is that two kinds of job screening procedures work reasonably well (but only about at the 0.5 level, standing alone). One is a general cognitive ability test (an IQ-like test, such as the Wonderlic personnel screening test). Another is a work-sample test, where the applicant does an actual task or group of tasks like what the applicant will do on the job if hired. Each of these kinds of tests has about the same validity in screening applicants for jobs, with the general cognitive ability test better predicting success for applicants who will be trained into a new job. Neither is perfect (both operate at about 0.5 level in validation studies), but both are better than anything else that has been tested in rigorous research, across a wide variety of occupations. So if you are hiring for your company, it's a good idea to think about how to build a work-sample test into all of your hiring processes. For legal reasons in the United States (the same consideration does not apply in other countries), it is difficult to give job applicants a straight-up IQ test (as was commonplace in my parents' generation) as a routine part of a hiring process. The Griggs v. Duke Power, 401 U.S. 424 (1971) case in the United States Supreme Court http://scholar.google.com/scholar_case?case=8655598674229196978&q=Griggs+Duke+Power&hl=en&as_sdt=2,24 http://scholar.google.com/scholar_case?case=8655598674229196... held that cognitive ability tests used in hiring that could have a "disparate impact" on applicants of some protected classes must "bear a demonstrable relationship to successful performance of the jobs for which it was used." In other words, a company that wants to use a test like the Wonderlic, or like the SAT, or like the current WAIS or Stanford-Binet IQ tests, in a hiring process had best conduct a specific validation study of the test related to performance on the job in question. Some companies do the validation study, and use IQ-like tests in hiring. Other companies use IQ-like tests in hiring and hope that no one sues (which is not what I would advise any company). Note that a brain-teaser-type test used in a hiring process might be illegal if it can be shown to have disparate impact on some job applicants and is not supported by a validation study demonstrating that the test is related to successful performance on the job. Companies outside the United States are regulated by different laws.

b0sk 14y ago

A contrarian p.o.v: They are going to lose out on exceptional cases where the candidate is a great engineer but is not able to devise a strategy towards a solution. However, there is a huge correlation between a good engineer and the ability to arrive at the solution (keep in mind they look at how you arrive at the solution too) Personally, I'd make the candidate solve a decent intermediate level problem using a computer (and Google too). Give him/her the closest approximation of the typical job environment.

mgkimsal 14y ago

I've had a few of these in my time, and I think, to an extent, they're legit, and I'll explain why. I was asked once - "how many gas pumps are in Raleigh?". I asked back "do you mean pumps for the general public, or do we need to include commercial/industrial pumps too?" and "do you actually mean Raleigh proper or the metro Raleigh area? if so, how do we define that? All of the county?" Next question was "go to the whiteboard and design a house". I took out the marker, started to draw, then turned and asked "who will be living there? Is this a single family or duplex? mobile home? stick built or modular?" and a couple other questions. I was told I was the first people to ask questions before drawing. I take the point of the brainteaser-type questions to be "how do you react to issues that come up where you don't know a lot of stuff?". For some positions, this is less important, but if you're a customer-facing position - even in development, you may interact with customers or other business units - how do you react when you get odd-ball "left field"-type questions? Do you keep your cool? Do you just react and say "that's stupid!"? Do you walk out in protest? Do you probe for more detailed information before making a pronouncement? More than ever, I think 'brainteaser' questions are far more about personality-judging than intellect or even raw "problem solving" ability.

msprague 14y ago
Yeah, I agree with this. I've been asked a similar problem to the gas pump one and a brain teaser one as well. The goal for them is to be able to get a better feel for how you deal with the problems, not necessarily the solutions that you come up and how accurate they are. Being a dick to an interviewer (as basically suggested in comments above) is great if you like being unemployed.
- mgkimsal 14y ago
  Additionally, though (and I think you're saying this), it's not just how you come up with a solution from a technical/procedural standpoint. It's more - how do you react in situations that are outside of your comfortzone? And as you said, being rude to an interviewer is a sure way to stay outside their company.