Over the last few years I've spent more time interviewing than being interviewed, so I sympathize with these questions. Questions of the form "How many X are t

Over the last few years I've spent more time interviewing than being interviewed, so I sympathize with these questions. Questions of the form "How many X are there in Y" are vanilla sizing questions, which are not first-order relevant for coding but are crucial for even the most basic engineering. The notion behind these questions is that an interviewee should be able to take a topic they're nominally familiar with (their favorite beverages, their home state), find a candidate correlation, and extrapolate (there are Y million people in my state, and the average consumer consumes X beverages per unit time, so XYtime). Questions of the form "You have X consumable Ys, how do you accomplish task Z within those X Ys", also wordable "how few consumable Xs do you need to accomplish Z" are about resource allocation or consumption, and are frequently used to ask questions about O-notation without using formulas or having programming/scripting interviewees tell you "oh I don't remember how to write bubble sort... but that's OK because every library has all kinds of sorts now" or to find out if system administrator candidates know about automation tools and how to apply them. The questions are very much not about rote memorization of brain teasers, and if the interviewer can sniff that behavior out it's _very_ negative: the interviewer most probably has no interest in the number of gas stations in Texas and will never be at the leaning tower of Pisa with two lightbulbs and an afternoon to spend. The idea is to ask one question that can test: 1) a candidate's willingness to pick up a new or unusual challenge 2) their ability to adapt what they're familiar with to solve a problem that they don't know off hand 3) the thought process involved in arriving at the conclusion Studying a list of "brain teasers" and their answers is like attempting to study a test's answer key -- it may get you through the door but it's very dishonest and a disservice to yourself as you cheat yourself out of an opportunity to expand your mind in a very relevant way using facts that aren't directly related.