4 ms·
“Knowing that 200 undersea cables break every year globally, estimate the probability that 3 cables break in the baltic sea on the same day.” I’m stealing this
by CrazyCatDog 2y ago
“Knowing that 200 undersea cables break every year globally, estimate the probability that 3 cables break in the baltic sea on the same day.”
I’m stealing this to use for grad-student mock-interviews—thank you!
- deleted 2y ago[deleted]
- Moru 2y agoHint: The cables are often very close. If one breaks, the otherone also breaks :-)
- gitaarik 2y agoWhy would cables close to each other break?
- leovingi 2y agobecause if it's an accident and someone is dragging an anchor behind them, if the cables are only meters apart then they are going to cut both
- 0points 2y ago[flagged]
- jeltz 2y agoNo, because anchors can easily damage several cables close to each other. And that is how it almost certainly happened no matter if it was an accident or sabotage.
- CrazyCatDog 2y agoRight, if it’s a case interview, then higher accuracy ought to prompt the interviewee to ask: (1) Do the 200 cuts typically occur in clusters? (2) What’s the typical density, eg are they usually collocated? (as an alternative to the above) (3) Are there pathways that avoid the sea but connect Europe and North America (getting at density in the sea in question) Etc. That’s what makes this one so good—lots of opportunities to extend or roll-back difficulty.
- ValentinA23 2y agoI was surprised to see so many upvotes this morning and was disappointed when I realized it wasn't for another comment I made about the Anthropic Principle. My take is that in face of coincidences supporting the emergence of intelligent life, we should expect to observe coincidences unnecessary for the emergence of life too. An analogy: imagine you have lost the key to your mansion and try to cut one at random out of a metal sheet. If it can unlock the door, then chances are that you cut unnecessary notches (the analogy only holds for warded locks and the key you crafted is a master key). See: https://news.ycombinator.com/item?id=42178306 https://news.ycombinator.com/item?id=42178306 I'm wondering where I'm wrong in my reasoning because the implication is weird.
- usrusr 2y agoWhat are the chances that they break in close proximity spacially, but not temporarily? (I'm assuming that it would be headline material if the lines had disconnected within minutes) Tangent: an attacker trying hard to provoke that kind of accident would likely not have a very fast success feedback. "Let's try once more, for good measure"
- crote 2y agoStill pretty decent, given the right circumstances. For example, the 2011 earthquake in Japan resulted in damage to 7 cables[0]. But it wasn't the quake itself which instantly broke all 7 cables - they were destroyed by underwater avalanches triggered by the earthquake. Avalanches can occur hours after a seismic event, and some underwater avalanches go on for days. I highly doubt that's the case here, but if you're asking about chances it's not as unlikely as you'd think! [0]: https://www.theverge.com/c/24070570/internet-cables-undersea-deep-repair-ships https://www.theverge.com/c/24070570/internet-cables-undersea...
- Cthulhu_ 2y agoA clever answer would be "it's a 50/50 chance, either it happens or it doesn't". That's statistics my simple brain can comprehend at least.
- kqr 2y agoIn what way is that clever? It's clearly wrong. If it were true, we'd experience three breakages at least 150 days of the year, every year.
- rrr_oh_man 2y ago[flagged]
- kqr 2y agoI think it is in the spirit of Hacker News to explain rather than just whoosh someone.
- rrr_oh_man 2y agoYou're right, that was not kind. Apologies. It was late at night and I'd read too many depressing news (and many even more depressing, warmongering comments). Not an excuse, just a human factor. What I should have said: By clever GP most probably meant funny (with a hint of self-deprecation) rather than smart (or even correct).
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- deleted 2y ago[deleted]