Brain Easer’s guide to brain teaser interview questions
What Are Brain Teasers
Brain teasers can be thought of broadly as types of puzzles that test problem-solving and critical thinking, and potentially other related skills such as logic, math, and creativity.
The Goal of Brain Teasers
An interviewer may ask a brain teaser to see how you would approach a problem or challenge, and to assess your critical thinking skills and how you think under pressure. Some brain teasers also test your ability to be flexible, creative, and adaptable.
Types of Interviews with Brain Teasers
You will most commonly encounter brain teaser interview questions in these industries or roles:
- Quantitative finance – including institutional and prop trading, hedge funds, quant trading and modeling
- Consulting – including management and strategy consulting
- Engineering interviews – including software engineering and data science & analytics
Back in the day, Google and Microsoft were notorious for asking brain teasers, and every trader interview featured a brain teaser.
In recent years, brain teasers have largely fallen out of favor with interviewers, partly because they are now considered a poor way to assess on-the-job performance. But you may still encounter them for certain roles and firms, so read on and learn how to prepare!
2. How to Prepare
To prepare for brain teaser interviews, understand the types of brain teasers you are likely to encounter in an interview, and train with practice problems.
Types of brain teasers
As the name suggests, logic puzzles test logical thinking and deduction, and usually feature multiple logical steps in which you use clues to rule out certain possibilities to arrive at a clever and tidy solution.
Often encountered in: finance interviews, some consulting interviews, and software engineering interviews.
Example: There are three boxes: one with two red widgets, one with two blue widgets, and one with one red and one blue widget. All three boxes are labeled incorrectly. What is the fewest number of widgets you have to take out in order to correctly re-label all the boxes? See the solution here
There are many types of math puzzles, but interview brain teasers most commonly test probability because it can be relevant to a lot of technical jobs.
Often encountered in: technical finance interviews, software engineering, and data analytics interviews.
Example: In a best of 3 tennis match, the player that first wins 2 sets wins the match. For a 3-set tennis match, would you bet on it finishing in 2 or 3 sets? See the solution here
Estimation problems test your ability to estimate some unknown value using limited information – typically solved by using some common knowledge and piecing together reasonable assumptions to arrive at a good estimate. These don’t usually have a single correct solution, the interviewer just wants to see if you can figure out what information you can bring in and apply to make a difficult problem a more tractable one.
Often encountered in: strategy/management consulting interviews (which often frame them in terms of “market-sizing questions”).
Example: How many people in Germany have iPhones?
While there is technically a correct answer, there isn’t just one correct solution – the idea is to identify relevant pieces and put them together logically. One potential approach is to break down the problem into a couple of steps like this: (1) rough population of Germany, (2) smartphone ownership rates, (3) iPhone market share (you may have a general sense and a guess as to whether that share might be higher or lower in Germany).
Riddles use a cryptic clue to describe an item or concept that you must guess. These often require some lateral and creative thinking.
Our take: riddles do not belong in interviews, but that doesn’t stop interviewers from asking them! These are uncommon precisely because they are not good at testing critical thinking, but in some cases they can be suitable for testing more creative types of problem-solving, like forensic investigation. We would recommend not using these to prepare, unless you have reason to believe a particular interviewer or company asks these.
Example: What is black when you buy it, red when you use it, and gray when you throw it away? See the solution here
Prepare by practicing
Prepare with lots of good practice problems. The key to becoming proficient at pretty much anything is to practice. For brain teaser interviews, make sure to practice with suitably difficult questions that may get asked in an interview.
Don’t waste your time with super easy brain teasers (you’ll get them anyway), or the wrong kind of brain teaser.
If you just search up “brain teasers”, you might come across unsuitable brain teasers like this:
How far can a squirrel run into the woods?
The answer is: halfway – after that, the squirrel is running back out of the woods.
While this is a clever and cheeky brain teaser, it isn’t a brain teaser that you are likely to encounter in an interview.
Start with Brain Easer’s curated collection of interview brain teasers, which feature puzzles that are suitable for interviews, many of which are sourced from actual interviews. The logic and math puzzles with more than one insight or logical leap are particularly suitable for interviews, because an interviewee can make progress and demonstrate their critical thinking skills even if they don’t arrive at the final answer.
3. How to Approach the Interview
Get comfortable with how to approach solving brain teasers at an interview. These steps may help you effectively tackle other types of interview questions as well.
A. Clarify the question
You need to fully understand the question in order to come up with a good solution. Ask clarifying questions.
B. Talk through your reasoning
Always talk through your reasoning, for a number of helpful reasons:
- You don’t necessarily need to correctly solve the brain teaser to do well, you just need to demonstrate how you would tackle a difficult problem. This is like getting partial credit in school for showing your work.
- Talking through your reasoning can buy you some time to think, and for some people it also helps organize your thoughts.
- This gives the interviewer an opportunity to steer you off the wrong track. You may misinterpret a piece of information or make an invalid assumption, and if the interviewer is able to jump in to correct your assumptions, you will waste less time.
C. Organize your solution
Remember that this is still an interview. While the brain teaser tests your critical thinking, you also should demonstrate other relevant skills to the job, such as organization, communication, and presentation.
So after you piece together the answer, organize your thoughts and clearly present the steps of your solution.
D. Impress the interviewer (optional)
If you’ve already solved the brain teaser, there is room to go above and beyond! If you have time left over, you can talk about variations and extensions on the brain teaser. Proactively solving a more difficult problem is likely to impress any interviewer.
Example: You and a friend play “first to 100”, a game in which you start with 0, and you each take turns adding an integer between 1 and 10 to the sum. Whoever makes the sum reach 100 is the winner. What is the winning strategy? See the solution here
But after getting the right answer, you might add a restriction – neither player is allowed to add 11 minus what the other player just added – and show that there is still a (different) guaranteed winning strategy.
Naturally, this is difficult to do, so don’t worry if you are not able to.
Another way to engage meaningfully with the brain teaser after you’ve solved it: to discuss why it was interesting to solve and how it might relate to the type of work you would do on the job.
At the end of the day, brain teaser interview questions are like any other interview question – an opportunity to demonstrate why you are a good candidate for the job. Hopefully this guide helped take some of the pressure off solving the brain teaser itself and will allow you to put your best foot forward at the interview.
Solve some practice brain teasers now!