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Comment by rocket_woman | Hacker News Reader

If the stuff online on Quora etc. are to be believed, the hiring committee will disregard such trivia interviews (and possibly send a node to the interviewer asking him/her to correct their technique).

Not sure how well this works in practice though.

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Last time I was job-hunting I experimented with Google to see if their interviews were as bad as everyone said.

They were. I was asked a ton of this kind of Linux/Unix trivia in one session. As well as just random stuff. For example:

https://twitter.com/ubernostrum/status/659182356171874304

https://twitter.com/ubernostrum/status/659182564309995520

https://twitter.com/ubernostrum/status/659182708996706308

Another way to answer this kind of question is to know 2^24 = 2^10 * 2^10 * 2^4 and that 2^10 is 1024 which is roughly 1000.

So 1000 * 1000 * 16 = 16 million would be an easy estimate to make.

If you are designing a system and want to have an idea of how much space or memory an approach will take, being good at this kind of math can be really helpful.

Then they should probably ask people to estimate a thing that's even remotely relevant to the job.

(I mean, I get it, this kind of general estimation and/or ball-parking can be incredibly valuable, but this doesn't sound relevant in any way.)

This kind of general estimation and/or ball-parking can be incredibly valuable, but this doesn't sound relevant in any way.

To be fair to Google (in regard to this one filter question only), they actually are up front about expecting a significantly higher baseline of general mathematical awareness (even for non-mathy roles) than most other shops. At any rate, this kind of estimation comes up in capacity planning (both in architecture planning, and for algorithms on a single box) all the time. Which after all is what Google does, at nearly every level of their stack, (nearly) all the time.

It "comes up all the time"... and these ballpark guesses are probably(!) completely useless for anything remotely practical. At the scale Google's operating you want a Statistician, not a Guesstimator.

So, no, still not useful questions.

The problem is that there are some people who will need to go through that process in their head to produce an estimate of 16 million - and then there are people who have had cause at some point in their life to know of the existence of the concept of '24 bit color' and that the number of colors expressible in 24 bits (8 bits each of R, G and B) is exactly 16,777,216.

The question there was something like "roughly how big is 2^24?". I actually think that's a reasonable enough question, but anyway there's a nice story about this same question in another context. The mathematician Solomon Golomb was (as an undergraduate, I think) taking some sort of biology class, and the lecturer described some process to do with cell division and said "... so the number of ways to do that is 2^24, and we all know that that is, don't we?" (meaning, of course, "and no one knows what that is but it's OK because I'm about to tell you". But Golomb happened to have been memorizing numbers of the form n^n, and 2^24 = 8^8, so he immediately called out "Yes, it's 16777216".

As a result of having read this story, I can now always instantly remember what 2^24 is too :-).

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