9 Steps to Solve Any Interview Brainteaser
âHow much does a school bus weigh?â
âHow many people are currently online in Germany?â
âHow many windows are there in New York City?â
And, most importantly: âHow the heck do you answer these crazy questions?â
Because if youâre interviewing for a tech job, chances are youâll get thrown one of these curveballs at some point during the selection process. And when you do, you donât want to totally whiff.
So to make sure that youâre ready to handle just about anything, let me share 9 steps that helped me [earn offers at Apple, Amazon, Microsoft, LinkedIn, and VC-backed startups]
1) Understand What the Interviewer Wants
Itâs easy to get flustered if you assume that this is the same kind of question you might find on a multiple-choice test â i.e., thereâs one right answer and lots of wrong ones.
Instead, think about it from the interviewerâs perspective. She needs to find someone who can succeed in this job â not someone whoâs great at counting windows. So what she really wants to know is whether you can handle the rigors of a crazy tech job:
⢠Dealing with uncertainty
⢠Thinking analytically
⢠Communicating clearly
Thus, take a deep breath and focus on demonstrating your curiosity, logical analysis, and clear communication â not on the answer itself!
To demonstrate your curiosity, start by asking some clarifying questions. For instance, if youâve been asked how many windows are in New York (PS: [hereâs a list Iâve collected of other tech brainteasers], you might respond by asking:
âWhen you say windows, do you only mean building windows or are you also thinking of subways, computers, and exhibits at the Bronx Zoo?â
This not only shows off your curiosity; it can also save you tons of agony. Because if it turns out that your interviewer only cares about building windows, this question just became a whole lot simpler.
Now, as tempting as it might be to dive right into calculations, resist that temptation. There are few people in the world who can write an essay AND read it aloud simultaneously. But thatâs exactly what you end up doing when you try to answer the question immediately.
So instead, ask for a few minutes to gather your thoughts and then jot down a quick outline like this one:
Apartments: 3 windows/person
Residential: 10M X 3 windows/person
That way, you get both the time to think analytically and the organization to communicate clearly. And no, interviewers arenât going to mark you down for taking a timeout. Because, again, they need someone who can do the job â and very few tech jobs involve solving brainteasers live, on-stage!
With your outline in-hand, itâs time to give your interviewer a roadmap to your answer. Thatâs because so many answers go off the rails when you think youâre being clear but the interviewer is totally lost.
âOK, so Iâm going to solve this problem in three steps. First Iâm going to name my assumptions. Next, Iâm going to break the problem into relevant categories. And finally, Iâm going to make calculations for each category.â
Now, the interviewer can keep track of your progress at every step (âOK, she just laid out her assumptions. Check!â). And, as a bonus, you come across as way more organized and analytical.
5) State Your Assumptions
As mentioned up-front, these questions rarely have one right answer. I mean, even the mayor of New York doesnât know exactly how many windows are in his city!
So instead of getting caught up in the search for an illusory truth, just make some logical assumptions. And then, most importantly, name and justify your assumptions.
For instance, you might say:
âWhen it comes to apartment windows, Iâm going to assume that there are three windows per resident. Thatâs because Iâve lived in a lot of two-person apartments that had six windows, on average. And so three per person feels about right.â
While this might seem like relatively flimsy evidence, the critical word here is âbecause.â Thatâs because psychology research has shown that people are significantly more likely to accept something with a justification attached. And it makes you look more organized,to boot!
6) Break the Problem Down
Now, these questions are often so massive that trying to solve them in one fell swoop can be downright ridiculous. So, instead, break them down into easy-to-digest parts.
In this case, you can offer an answer like this
âOK, since buildings in New York are so different, Iâm going to look at the three main categories of buildings separately: Residential, Retail, and Office.â
And now, the question that once looked freakishly scary has become quasi-reasonable â and you get to flex your analytical biceps.
While knowing that there were 8.406 million people in New York in 2013 might help you win Trivia Night at the demographersâ bar, trying to multiply 8.406 times anything is a recipe for disaster. So do yourself a big favor and round to the juiciest whole number you can think of:
âAlright, Iâm going to say there are about 10 million people living in New York, give or take a millionâŚâ
Again, no oneâs testing your Rain Man skills. And this will pay off big time when youâre ready toâŚ
It might feel safer to do your calculations in your head so the interviewer canât see your crummy arithmetic skills. But thatâs just nuts â again, who can pull off 27 different mental calculations while simultaneously obeying the 95 rules of interview etiquette?
So skip the Math Olympiad stuff and show your work on paper or a whiteboard, step-by-step:
âOK, there are 10 million people in NYC. So Iâm going to multiply that times 3 windows per person to get 30 million residential windows. Now letâs move on to retailâŚâ
Now, even if you do mess up, you have the visibility to stop yourself before your errors snowball into an avalanche.
So youâve finally reached an answer [see my complete solution and all my tech interview techniques here]. Congrats â youâre done, right?
Remember that these questions arenât about the answer â instead, theyâre about the process. So before you drop the microphone, take one last chance to show off your curiosity and analytical chops by caveating your answer:
âSo thatâs my answer. But Iâm not totally happy with it because I completely neglected development trends in the city. I basically assumed that every building was your typical old-school New York office or apartment, with relatively few windows. But all the new buildings are 100% glass, which suggests that this number is probably on the low side.â
And now, at last, youâre done. Which leaves you just enough time to figure out how much that school bus weighs after allâŚ
This is a guest post by Jeremy Schifeling, who is the Founder + Chief Nerd at Break into Tech, a site for anyone who wants to land an awesome tech job, no matter their background. Previously, Jeremy interned at Apple, hired at LinkedIn, and served as an executive at a VC-backed startup - all after starting his career as a kindergarten teacher! Get a free guide to the 7 ultimate secrets that took Jeremy from teaching to Silicon Valley right here