Interview brainteasers?

March 26, 2013 6:52 PM

I have an interview with a technology startup coming up that will involve "brain teasers". Got any tips or practice questions?

I'm not really looking for the riddle-esque "Microsoft-style" interview questions you see spammed all over the internet - I'm looking for questions geared towards evaluating quantitative reasoning/analysis and the ability to think logically on your feet. Also looking for tips to get into the right mindset for this kind of interview.

This is not a software development position, if it matters.

posted by hot soup to Work & Money (8 answers total)

I've heard of certain firms asking "guesstimation" style problems, like how many ping pong balls would fit in your car type of thing. There's an excellent book out there called Guesstimation (and its sequel, Guesstimation 2.0) that has a collection of these problems, hints, solutions, and techniques to solve them. It's actually really fun and if you have geeky friends it makes for good idle banter.
posted by neil pierce at 6:58 PM on March 26, 2013

In the same vein as what neil pierce mentioned, Fermi problems might be a good place to start too.
posted by un petit cadeau at 7:08 PM on March 26, 2013

Fill the container that holds 5 water units all the way up. Pour it into the other container that holds 3 water units until it's full, leaving 2 in the 5 container.

Pour the 2 units into the 3 container. Fill the 5 container full again, then pour water from the 5 into the 3 until the 3 is full. This removes 1 unit from the 5, leaving it holding 4 units, which is the goal of this cliched "brain teaser" that you will more likely than not be asked.
posted by drjimmy11 at 8:03 PM on March 26, 2013 [1 favorite]

Are you looking for the "think logically" type of brain teaser, where there is little to no technical background required to find the answer?

Or are you looking for the (in my opinion more common) technical interview brain teasers that require mathematical background, computability/complexity, clever data structures, etc?
posted by homotopy at 8:31 PM on March 26, 2013

There's a book called "Are You Smart Enough to Work for Google?" that would seem to fit the bill.
posted by TheSecretDecoderRing at 9:09 PM on March 26, 2013

Define what you know (note, not what you think; what you know). Define what you don't know. Define questions you can ask to get to what you don't know. Mark out any implicit assumptions. Add to the know or don't know list based on what you find out. Iterate until a solution is found.

Incidentally, this is the exact same methodology I use for troubleshooting thorny problems. I am a beast at troubleshooting.
posted by bfranklin at 5:19 AM on March 27, 2013

Talk through the problem.

1. "How many ping-pong balls fit in my car? Let's say a ping-pong ball is 1.25 inch in diameter for volume v. If I lean to the middle of my car, I can touch both windows, so inside width is 6'. Top to seat distance is probably x, back to front y, so volume is z. Seat back volume is approximately equal to footwell volume. Divide z by v, multiply by packing factor (about 2/3 for close-packed structures), answer is n."

2. (thinks for 20 s, stares into space) "n."

The first gives the interviewer a glimpse into your thought processes ("this person thinks analytically, states assumptions, lays out the data trail, and uses the information to calculate an answer which can be refined by checking each of the steps"). The second doesn't. In my experience, HR bots like the first, and technical persuns might be intrigued by the second, but they'll probably quiz you for the methodology you used.
posted by disconnect at 10:58 AM on March 27, 2013

Heard on the Street has lots of brainteasers with detailed explanations. It's geared toward finance but there are a lot of general brainteasers too.
posted by pravit at 3:46 PM on March 27, 2013