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Comment by frandroid | Hacker News Reader

A brain teaser usually has nothing to do with the work... What would asking about the shape of manhole covers have to do with OOP?

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The estimation question has real-world uses from figuring out market size to even large project effort estimation. Interviewer is looking to see if the candidate can break part a hard problem into smaller solvable sizes. A famous example is when Fermi estimated the size of atomic explosion by dropping pieces of paper during the blast.

https://www.quora.com/How-did-Fermi-estimate-the-power-of-th...

The theory would be that it allows the interviewee to demonstrate abstract reasoning skills, which are useful in many domains.

Also the interviewee needs to have exactly the same assumptions about the world as interviewer (or whoever come up with the brainteaser) and the knowledge of the same basic facts.

I mean how do you even approach questions like -- how many snowflakes on the south pole? how many fish in all of the oceans? how much grass is in Mongolia?

I think that's the point of the question: to see how you approach it. The 'correct' approach that they'd be looking for is 'Fermi estimation': https://en.wikipedia.org/wiki/Fermi_problem

No, the point is to try to rationalize cargo-culting. Fermi did this, and Fermi was brilliant, so if we require candidates to do this we'll end up hiring people who are as brilliant as Fermi!

Here's a brainteaser: spot all the flaws in that chain of "reasoning".

Um, no. It's not cargo-culting. It's the correct way of estimating things. It has nothing to do with Fermi having done it. Some things actually have correct answers. 2 + 2 = 4, is not cargo culting.

You just moved the goalposts from looking for "a Fermi estimate" to looking for a correct answer.

Um...no. The goalposts have always been that the purpose of the brainteasers was to demonstrate reasoning skills. Using Fermi estimation is demonstrating reasoning skills. It's not like some trick that you have to know, it's not a formula. It's something any intelligent person would do on their own when faced with a task of this sort.

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