How to answer brain teasers in interviews for Consulting & Investment Banking jobs

If you thought that interviewers at management consulting and investment banking (IB) interviews use brainteasers to put candidates at ease and bring in some light-hearted moments, you will be scratching your head after reading this: these mindbenders have a larger purpose.

Although brainteasers may not be such a key part of interviews as technical and cultural fit questions, they help interviewers sort out the best from a lot of equally good candidates.

Interviewers use brainteasers as another test of your analytical ability. They come up with these quirky puzzles to assess your creativity, or how well you can think outside the box.

Brainteasers help them evaluate your problem-solving skills, your ability to think on your feet and come with solutions to problems quickly, your capacity to work under pressure, your ability to structure your thoughts, your analytical skills, and your critical thinking skills. That’s how useful they are to interviewers.
 

How to answer brain teasers in interviews for Consulting & Investment Banking jobs

Here are some tips and techniques to crack brainteasers at consulting and I-Banking interviews.
 

Take your time

The first good advice is that you should take the time to understand the question or the brainteaser.

Don’t rush it. Don’t panic and lose your focus, and don’t blurt out the first answer that comes to your head.

Consider the brainteaser as an important life situation that you need to solve, and approach it calmly.

Interviewers will try to find out whether you lose your cool, which a good banker cannot afford to do.

It is all right to say, “Can you give me a minute to gather my thoughts?”

You will not be losing any points for taking some time. The interviewer has herself gone through your situation before and is not trying to browbeat you with a brainteaser.
 

Ask follow-up questions

After understanding the brainteaser, you may find that there are some information gaps in the question that you what clarity about.

A good way to show the interviewer that you are trying to understand the question and approaching it logically is to ask follow-up questions.

For example, take the classic question, “How many golf balls can fit in a Boeing 747?”

You could respond with follow-up questions such as whether there are passengers in the aircraft and whether the cabin is pressurized.
 

Articulate your thoughts

Answers to some brainteasers may be counterintuitive. Some of these mindbogglers may not have a definitive answer at all.

A well-kept secret is that interviewers are not looking for exact answers to brainteasers.

They are interested in how you approach the question, that is, they are trying to map your thought process and how you proceed from understanding the problem to finding a solution.

A good way to impress them is to articulate your thoughts even as you are trying to find the answer, so that the steps you take to find an answer are clear to the interviewer.

So, think out loud. Interviewers will give you the thumbs up if they see that can approach complex problems in a logical way, which means that you have the ability to understand business models, which is crucial in an investment banking job regardless of whether it’s a top bulge bracket bank or a boutique firm.

If you are using a paper and pencil to actually work out the answer, be sure to show your work to the interviewer as you go along.

Another advantage of thinking out loud is that the interviewer may subtly correct you if you go wrong in the process of finding a solution or he may give you a sign that you are going wrong.

If this happens, you may have the chance to do some course correction and think of another approach to solve the question.
 

Have a conversation

Adding to the point about thinking out loud, you should remember that the interview is a conversation. The interviewer is trying to find how interesting you are as a person.

As part of the conversation, you could explain rationally to the interviewer how you are going to solve the brainteaser and whether she thinks it is the right approach.

If you are completely clueless, you could even ask what would be the best approach. If you missed the trick completely, be sportive enough to admit it.

By handling the question level-headedly, you have taken the first step to solving it, and shown yourself as capable of being proactive in a life situation.
 

Show your personality

Show that you are enthusiastic, curious, and cool-headed. Don’t get tense and flustered and struggle to get to the answer quickly to impress the guy across the table.

It is a good idea to be prepared by practising solving brainteasers, although you would be lucky to have a familiar brainteaser thrown at you during an interview.

Practice may give you a few tips and may put you at ease when you are trying to solve a brainteaser at an interview.
 

Don’t obsess

Someone knowledgeable says you should not get obsessed with preparing for brainteasers.

Some people say brainteasers are more likely at sales and training interviews these days than at consulting and IB interviews, and that bank interviewers have moved on to other methods such as guesstimate cases and business-situation cases.

However, many firms continue to repose faith in brainteasers as an interviewing tool. But they are unlikely to be a game-changer at a banking interview.

However, if you are interviewing at an elite boutique or group or firm that is known to use brainteasers, yes, by all means, get a book or go online to prepare, says a Wall Street expert.
 

Have fun

One tip that you should never forget is to have fun trying to solve a brainteaser at an interview.

Remember that the interviewer is not expecting an exact answer. He may not know the answer himself and is really only interested in your approach to solving the question.
 

Types of brainteasers with examples

 

How many…

Brainteaser lovers say there are a few main types of these conundrums. The first is the “How many Xs in Y?” type.

Here are some examples:

• “How many domestic light bulbs exist in Mumbai?”
• “How many public payphones are there in New York?”
• “How many books are there in libraries in the UK?”

Remember that you can ask additional questions.

For example, in the questions about light bulbs, you could ask the interviewer to provide the population of Mumbai and go about making a guesstimate from this number.

No one would know the correct answer. But you could make a rational guess.
 

Riddles

Here’s an example for a riddle type brainteaser.

If a wheel has 32 spokes, how many spaces between the spokes would there be?

The answer is 32.

Or, what year of the 20th century and what year of the 19th century read the same when they are upside down?

The answers are 1961 and 1881.
 

Math brainteasers

Math brainteasers test your math skills, obviously, but mainly your statistical and probability skills.

For example, if you roll a pair of dice, what are the chances that the sum will equal 6? The answer is 5/36.

How? There are 36 likely outcomes from rolling a fair, six-sided dice. The outcomes that add up to 6 are 1,5; 2,4; 3,3; 4,2; and 5,1. You should show the interviewer how you went about solving the puzzle.

One more example: How much is 999 X 53?

You are not expected to work out the multiplication, and you are supposed to use a shortcut: “999” is 1,000 – 1. But 1,000 X 53 = 53,000. So, 999 X 53 is 53,000 – 53 = 52,947.
 

Logic brainteasers

This is the last type that we discuss in the article. Here’s an example.

What is the angle between the hour hand and the minute hand when the time is 9.30?

Hint: It is not 45 degrees!

The hour hand moves 360 degrees in 12 hours, which is 30 degrees per hour. Therefore, it moves 15 degrees in 30 minutes.

By 9.30, the hour hand would have moved 15 degrees away from “9”.

So, the answer is 90 degrees (the angle between “9” and “6”, where the minute hand stands at 9.30) plus 15 degrees, which is 105 degrees.
 
Your thoughts about how you responded to brainteasers at your interview can make you feel like you have ruined the whole interview or you have aced it, no matter how you might have done the rest of the interview.

Admittedly, you cannot prepare for every brainteaser: if you could, the questions wouldn’t be brainteasers at all. But you could familiarize yourself with them so that you are not caught unawares.

Also read:
– Interview questions for investment banking jobs
– Case interview sample question and answer tips – Mergers & Acquisitions
– Job interview tips for international MBA students
 
References: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11