30 Brain Teaser Interview Questions & Detailed Answers

If you have learned about consulting interviews, the term "Brain Teasers" is certainly familiar to you at some stage, however, are recruiters really using it in interviews or is this just a myth? According to a senior consultant/interviewer of McK and BCG, the use of brainteasers differs across the tiers:

• Not used in MBB
• Sometimes used in Tier 2 firms (Roland Berger, Oliver Wyman, etc.)
• Frequently used in Tier 3 firms (Arthur D. Little, etc.)

Brain Teasers are now being used less in interviews by consultants since they have recognized the limitations of brain teasers as an assessment tool and have shifted their focus to more practical case interviews that reflect the actual work of a consultant. 

However, not all consulting businesses share the same opinion. In fact, many consulting firms still utilize brainteasers to seek out candidates who are capable of thinking rationally and creatively under pressure. Hence, to best prepare for the interviews, you should learn something about this subject.

What are Brain Teasers in Consulting Interviews?

Brain teasers are “trick questions”

Brain teasers are puzzles or problems that require a candidate to use logic, creativity, and critical thinking to arrive at a solution. These quizzes come in various forms, such as math problems, logic puzzles, or situational challenges and also can be applied in a wide range of cases in different fields. 

Brain teasers aim to test the ability of people to think outside the box, analyze complex situations, and solve problems under pressure.

Brain teasers used to be important

According to former consultant of Accenture, brain teasers were used to be an important part of consulting interviews as they are not placed in a business setting so it can provide the company with insights regarding how applicants apply logic and creative thinking to solve problems outside of expertise areas. 

This can be necessary when assessing freshmen without much work experience, hence, it also allowed the employer to see how the candidates responded under pressure when confronted with a novel problem

Another reason is they provide a means of testing a candidate's analytical and problem-solving skills which is a critical skill for a consultant as they are often called upon to solve difficult business problems for their clients. They often involve a complex scenario or ambiguous problem that requires candidates to think outside the box or use data to make informed decisions. 

Additionally, brain teasers can also provide insights into a candidate's communication skills. Consulting firms tend to look for candidates who can not only solve complex problems but also communicate their thought process and reasoning successfully. 

As consultants must be able to convey their ideas to customers, coworkers, and stakeholders so the capacity to explain a solution succinctly and clearly is a requirement.

Examples of brain teasers used in consulting interviews

Examples of brain teasers used in consulting interviews vary in complexity and can range from simple math problems to more intricate logic puzzles. 

One example of a brain teaser is the "Three Light Bulbs Problem." In this scenario, a candidate is presented with a room containing three light bulbs and a single switch outside the room. 

The challenge is to determine which light bulb corresponds to which switch, using only one entry into the room.

Consulting firms may also present situational challenges as brain teasers.

For example, the "Airline Seating Problem" involves an airline flight with 100 seats and 100 passengers. The first passenger has lost their boarding pass and decides to sit in a random seat. Each subsequent passenger will either sit in their assigned seat or take a random unoccupied seat. 

The candidate must determine the probability that the last passenger will sit in their assigned seat.

Types of brain teasers you might face in consulting interviews 

There are seven common types of brain teasers that consulting firms may use in interviews.

Illusion question: 

Generating false impressions and focusing your attention on unimportant details and can lead you to miss the crucial information

Question 1:

Is it possible for a man in California to marry his widow's sister?

Question 2:

A farmer has 17 sheep and all but 9 die. How many are left?

Question 3:

How many two-cent stamps are there in a dozen?

Question 4:

If a doctor gives you three pills, telling you to take one every half hour, how many minutes will pass from taking the first pill to the last pill?

Question 5:

Two U.S. coins add up to 30 cents. If one of them is not a nickel, what are the two coins?

Answer 1:

No. The word “his widow” signifies that the man has died.

Answer 2:

9 sheeps. The question tries to lure you into calculating “17-9=8” when the answer is right there.

Answer 3:

12 stamps. You didn't try to multiply 12 with 2, did you?

Answer 4:

60 minutes. There are only 2 30-minute intervals, not 3.

Answer 5:

A nickel (5 cents), and a quarter (25 cents). This question tricks you into thinking neither coin is a nickel.

Draw-explanation question: 

Providing you with a peculiar and improbable situation, and you have to develop an answer that fully explains the circumstances

Question 1:

A doctor's son's father was not a doctor. How is this possible?

Question 2:

A woman and daughter walked into a restaurant. A man walked past and the women both said “Hello, Father”. How is this possible?

Question 3:

Donald brought his wife to the hospital because she was suffering from appendicitis. The doctors removed her appendix. Five years later, the very same Donald brings his wife in, again for appendicitis. How is this possible?

Question 4:

A horse jumps over a castle, then lands on a man. The man disappears. What's happening?

Question 5:

A man was born in 1945, but he's only 30 years old now. How is this possible?

Answer 1:

The doctor is the mother.

Answer 2:

The man is a priest, or his name is Father.

Answer 3:

Donald divorced and remarried.

Answer 4:

Chess.

Answer 5:

1945 was the number of the hospital room.

Wording question: 

Including at least one word that can be interpreted into multiple meanings as well as misleadingly suggested by the context, usually different from the default interpretation in your mind, makes the question inexplicable 

Question 1:

What two words, when combined, hold the most letters?

Question 2:

People who smoke are much more likely to develop lung cancer than those who do not smoke. What research would possibly show that cigarette smoking does not cause cancer?

Question 3:

Make one word from all the following jumbled letters: R E O D N O W

Question 4:

What kind of cheese is made backwards?

Question 5:

What has four legs but only one foot?

Answer 1:

“Post” and “office”.

Answer 2:

One that shows an indirect relationship between smoking and lung cancer, i.e “smoking causes X, X causes lung cancer”. The key here is to look at “cause” as a direct relationship.

Answer 3:

“One word”.

Answer 4:

Edam cheese.

Answer 5:

A bed.

Pattern/trend questions: 

Involve a series of numbers or letters with a certain pattern or trend and your task is to either identify the following thing or fill in the gap.

Question 1:

What is the next number in the following sequence: 0 0 1 2 2 4 3 6 4 8 5 ?

Question 2:

What is the next letter in the following series: Y Z V W S T P Q ?

Question 3:

Which verb does not belong with the others in this set?

BRING BUY CATCH DRAW FIGHT SEEK TEACH THINK

Question 4:

MUSIC : VIOLIN is similar to:

(a) notes : composer / (b) sound : musical instrument / (c) crayon : drawing / (d) furniture : carpentry tools / (e) symphony : piano

Question 5:

What is the next number in the following sequence: 125, 64, 27, 8?

Answer 1:

Number “10”

The sequence alternates between two different patterns:

Pattern 1: Incrementing by 1 (0, 1, 2, 3, 4, 5) 

Pattern 2:  Incrementing by 2 (0, 2, 4, 6, 8)

Answer 2:

Letter “R”

The series alternates between two different patterns:

Pattern 1: Moving two letters forward in the alphabet (Y, V, S, P ...) Pattern 2: Moving one letter forward in the alphabet (Z, W, T, Q ...)

Answer 3:

“THINK” is a mental process rather than a physical action

Answer 4:

(b) sound : musical instrument

Answer 5:

The next number in the sequence is 1=3^1.

125 = 5^3 

64 = 4^3 

27 = 3^3 

8 = 2^3

Logical questions: 

The least mind-bending format of them all, these questions typically don't include any creativity, illusions, or tricks, so you can solve them with just your pure math skills and logical reasoning.

Question 1:

A boy and a girl are sitting on a bench. “I’m a girl,” says the child with brown hair. “I’m a boy,” says the child with blond hair. If at least one of them is lying, which one is lying?

Question 2:

An explorer found a silver coin marked 7 BC. He was told it was a forgery. Why?

Question 3:

A bus can hold x people. It was half full from the start, and at the first stop, y people got off. How many people can now get on the bus?

Question 4:

What day follows the day before yesterday if two days from now will be Sunday?

Question 5:

During lunch hour a group of boys from Mr. Bryant’s homeroom visited a nearby grocery store. One of the five took an apple.

Jim said, “It was Hank or Tom”.

Hank said, “Neither Eddie nor I did it.”

Tom said, “Both of you are lying.”

Don said, “No, one of them is lying, the other is speaking the truth.”

Eddie said, “No, Don, that is not true.”

When Mr. Bryant was consulted, he said, “Three of these boys are always truthful but two will lie every time.”

Who took the apple?

Answer 1:

Both are lying. If any of them told the truth, they would deliver one same answer.

Answer 2:

Both are lying. If any of them told the truth, they would deliver one same answer.

Answer 3:

At the start, the number of vacant seats on the bus was x/2. After the first bus stop it becomes x/2 + y.

Answer 4:

Thursday. Today is Friday because “two days from now will be Sunday”. “day follows the day before yesterday” is just yesterday, so it’s Thursday.

Answer 5:

Tom took the apple

Jim Hank, and Eddie were telling the truth

Tom and Don were lying

Letter-trick question:

These questions are twisted which plays with the organization demonstration and composition of letters, forcing us to consider them from a variety of perspectives.

Question 1:

What does this mean? “GGES EGSG SEGG ESGG”

Question 2:

What does this mean? “ROFORKAD”

Question 3:

What does this mean? “CCCCCCC”

Question 4:

What does this mean? “F AST”

Question 5:

What does this mean? “GR 12” AVE”?

Answer 1:

Scrambled eggs.

Answer 2:

Fork in the road.

Answer 3:

Seven seas.

Answer 4:

Breakfast.

Answer 5:

One foot in the grave.

Market-sizing and guesstimate questions: 

Guesswork questions that require respondents to make predictions about a topic in a given area using data to make informed decisions, and  effectively convey their thought process. 

This is one of the most popular types of brain teaser questions and is still widely used by recruiters. To gain a better understanding of this particular queries, you might read the article: Market-sizing & estimate questions.

→ You can also learn more about these 7 types of questions and how to solve them in the video: Solving ANY Brain Teasers After This Video. For Real!

Why Consulting Firms rarely use Brain Teasers in Interviews now?

Unfortunately, a lot of consulting firms have shifted away from using brain teasers in their interview processes for a number of reasons. Firstly, brain teasers may test a candidate's analytical and problem-solving abilities, they do not necessarily reflect the types of problems that consultants face in their day-to-day work.

Secondly, brain teasers can be intimidating for candidates and may not provide an accurate representation of their abilities. Candidates who are perfectly capable of solving complex business problems may struggle with brain teasers simply due to the pressure of the interview environment. This can result in an inaccurate assessment of a candidate's abilities and potential, leading to missed opportunities for both the candidate and the consulting firm.

Lastly, consulting firms have recognized the importance of diversity and inclusivity in their recruitment processes. Brain teasers may disadvantage candidates who have not had the opportunity to develop specific skills or who come from non-traditional backgrounds. 

By focusing on case interviews, which present candidates with real-world business problems that they may encounter as a consultant, consulting firms can provide a more level playing field for all candidates, regardless of their background or previous experience. This type of assessment is more reflective of the skills and abilities required for success as a consultant.

How to succeed in Consulting Interviews' Brain Teasers section?

Five ways to practice for brain teasers in consulting interviews

Preparing for brain teasers in consulting interviews can be challenging, as they require a unique set of skills and abilities. However, with the right approach and practice, candidates can improve their performance and increase their chances of success. Below are some ways to practice for brain teasers in consulting interviews:

• Start with basic brain teasers: Before tackling more complex brain teasers, it's essential to start with basic puzzles and problems. This will help you develop your problem-solving skills and build confidence in your abilities.
• Focus on different types of brain teasers: There are many various types of brainteasers, such as word-based challenges, logical inquiries, and mathematics puzzles. Working on a number of different brainteasers to prepare yourself for the types of problems you may encounter in a consulting interview.
• Practice online resources: There are many online resources available that offer practice brain teasers and puzzles. Websites like BrainDen and Mentalup offer a variety of riddles and mental challenges, practicing in conjunction with Case Interview Programs will help you to be more equipped to handle a great situation during the interview.
• Time management: In a consulting interview, time is often a factor, and candidates are expected to solve problems quickly and efficiently. Practice timing yourself when solving brain teasers to improve your speed and accuracy.
• Practice under pressure: Consulting interviews can be high-pressure situations, and candidates may feel anxious or stressed during the interview process. Practice solving brain teasers under pressure to simulate the interview environment and prepare yourself for the real thing.

Five tips for solving brain teasers in consulting interviews

Similar to other tests and examinations, the brain teaser in consulting interviews also has some helpful tips to use. Some resharpers that may improve candidates' performance include:

• Read the problem carefully: The key to solving brain teasers is to understand the problem fully. Read the problem carefully, and make sure you understand what is being asked before attempting to solve the problem.
• Break the problem down: Brain teasers can be complex and challenging, but breaking the problem down into smaller parts can help make it more manageable. Identify the key elements of the problem and work on solving each element individually before putting them together.
• Use logic and reasoning: Try to use reasoning and creativity as you go through the brainteaser to come up with solutions. This may involve attempting different approaches, speculating, or using your understanding of science, math, or other disciplines to assist in solving the issue.
• Draw diagrams and visualize the problem: Drawing diagrams and visualizing the problem can help you understand the problem better and find a solution. Use it in a way that helps you see the problem from different angles and perspectives.
• Think outside the box: Brain teasers are designed to be challenging and require creative thinking to solve. Don't be afraid to think outside the box and explore unconventional solutions to the problem.

Four common mistakes when solving brain teasers during interviews

Nevertheless, there are some common mistakes that inexperienced candidates often have, preventing them from performing to their full potential. Here are a few things to steer clear of during the interview:

• Making assumptions: Brain teasers often require candidates to make assumptions, but it's essential to make only necessary assumptions and not make assumptions that are not supported by the problem.
• Explaining your thought unclearly: In a consulting interview, showing your thought is just as important as getting the right answer. Show your work and explain your thought process to demonstrate your problem-solving skills.
• Rushing to a solution: Time is often a factor in consulting interviews, but rushing to a solution without fully understanding the problem can lead to mistakes and errors.
• Overcomplicating the problem: Don't overcomplicate the problem by adding unnecessary complexity. Stick to the basics and use common sense to arrive at a solution.