These “think-out-of-the-box” interview questions are the least predictable kind among 8 types of questions . For these questions, you need a natural talent… or at least that’s what many people say.
I believe that even these seemingly unpredictable brain teasers can be trained for with a rigorous, systematic approach, and I’m going to show you how.
What are brain teasers?
Brain teasers are riddles and puzzles that require quick, intensive, unconventional thoughts. They are used in interviews to assess the candidate’s “out-of-the-box” and logical thinking capacity. Most brain teasers can be assigned to a few types with the same logical basis.
Brain teaser interview question examples:
- What kind of bank has no money in it?
- What has a bed but never sleeps?
- How many golf balls can fit inside a Boeing 747?
Why do interviewers ask brain teaser questions?
Interviewers ask brain teaser questions to test the candidate’s ability to think logically and creatively, as well as dealing with a difficult situation under pressure. Candidates not only need to think “out-of-the-box”, but also deliver the answer in a calm, collected manner.
Even though the use of brain teasers have been decreasing, there is still a chance of them appearing in consulting case interviews, as one of the seven possible question types. If you want to learn about all of these question types (brain teasers included), you can check out this general guide on Case Interview Questions.
How can you prepare for brain teaser questions?
The key to conquering case interview questions, including brain teasers lies in breaking down the questions into specific types, then preparing for each type accordingly.
Most brain teasers can be allocated into these seven types:
- Illusion Brain Teasers
- Draw-Explanation Brain Teasers
- Wording Brain Teasers
- Pattern/Trend Brain Teasers
- Logical Brain Teasers
- Letter-Trick Brain Teasers
- Market-Sizing & Guesstimate Questions
I’ll walk you through each type and show you how to nail each of them consistently. There will also be 30 examples for you to practice with, along with tips and tricks to handle the questions and present your answers impressively.
End-to-End Secrets Program
- 10 case interview Tips & Techniques videos
- +1,400 Consulting Math questions
- 60+ Business Intuition exercises
- PEI & Fit Interview deep-dive guide
1. Illusion Brain Teasers
These questions trick you into wrong conclusions by drawing your attention to seemingly interesting but insignificant and misleading details.
To avoid that trap, pay close attention to every detail of the question – that way, you’re more likely to notice actually-important details.
Tracy’s mother has four children. One child is named April. The second one is May. The third is June. What‘s the fourth one’s name?
The correct answer is “Tracy”. The question tricks you into believing the fourth child is named “July” following the very obvious pattern of April-May-June.
Questions and answers
Is it possible for a man in California to marry his widow’s sister?
A farmer has 17 sheep and all but 9 die. How many are left?
How many two-cent stamps are there in a dozen?
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?
Two U.S. coins add up to 30 cents. If one of them is not a nickel, what are the two coins?
No. The word “his widow” signifies that the man has died.
9 sheeps. The question tries to lure you into calculating “17-9=8” when the answer is right there.
12 stamps. You didn’t try to multiply 12 with 2, did you?
60 minutes. There are only 2 30-minute intervals, not 3.
A nickel (5 cents), and a quarter (25 cents). This question tricks you into thinking neither coin is a nickel.
2. Draw-Explanation Brain Teasers
This type of question gives you “weird” and seemingly impossible situations, then asks you to explain that situation.
For this one, you need to be creative and imaginative. Don’t be afraid of delivering “weird” answers – the question is already weird, to begin with; your answer only needs to fit with that universe.
A man is lying dead in the middle of a forest, in the middle of a puddle, in a scuba suit.
How did he die?
A tornado sucked him up from the ocean and threw him into the forest.
The saying “If it’s stupid but it works, it ain’t stupid” really does apply to these questions.
Questions and answers
A doctor’s son’s father was not a doctor. How is this possible?
A woman and daughter walked into a restaurant. A man walked past and the women both said “Hello, Father”. How is this possible?
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?
A horse jumps over a castle, then lands on a man. The man disappears. What’s happening?
A man was born in 1945, but he’s only 30 years old now. How is this possible?
3. Wording Brain Teasers
These questions confuse you by using seemingly conflicting words to create inexplicable scenarios.
The key to solving them is to doubt your first interpretation of every word in the question, then actively find other meanings that make the scenario possible.
You walk across a bridge and you see a boat full of people yet there isn’t a single person on board.
How is that possible?
Because they’re all married. The word “single” is the tricky one.
Questions and answers
What two words, when combined, hold the most letters?
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?
Make one word from all the following jumbled letters: R E O D N O W
What kind of cheese is made backwards?
What has four legs but only one foot?
4. Pattern/Trend Brain Teasers
This kind of question presents data (often numbers) following certain patterns or trends and demands you to fill in the blanks.
If you’ve given such questions, try to take different angles, find as many trends as possible, and check if those trends actually fit the data.
Two more points to keep in mind: (1) in many cases, the correct trend is not obvious, and (2) it’s fine to come up with something different from the interviewer’s mind, as long as it works.
What’s next in this series: 2, 4, 12, 48, …?
One fitting answer is 240 – with the exception of the first one, each number in the series is formed by multiplying its position with the previous number (4 = 2 x 2, 12 = 3 x 4, 48 = 4 x 12, 240 = 5 x 48).
Questions and answers
What is the next number in the following sequence: 0 0 1 2 2 4 3 6 4 8 5 ?
What is the next letter in the following series: Y Z V W S T P Q ?
Which verb does not belong with the others in this set?
BRING BUY CATCH DRAW FIGHT SEEK TEACH THINK
MUSIC : VIOLIN is similar to:
(a) notes : composer / (b) sound : musical instrument / (c) crayon : drawing / (d) furniture : carpentry tools / (e) symphony : piano
What is the next number in the following sequence: 125, 64, 27, 8?
10. There are two alternating sequences: 0, 1, 2, 3, 4, 5 and 0, 2, 4, 6, 8.
M. Letters are in pairs, backwards skipping every third letter: M N (O) P Q (R) S T (U) V W (X) Y Z.
DRAW is the only verb on the list with a past tense that does not rhyme with OUGHT.
(d) furniture : carpentry. The second word denotes the tool used to make the product in the first word. (note that musical instruments are used to make music, not just any sound).
The answer is 1. The cube-roots of the four given numbers are 5, 4, 3, 2 respectively, so the next one should have its cube-root being 1.
5. Logical Brain Teasers
Logical brain teasers involve no tricks, illusions, or creativity. You have to rely on the logic muscles of your brain.
Let’s try out one example:
You are presented with two doors – one leading to Freedom, the other to Death. Each door has a guard, with one always lying and the other always telling the truth. For both the doors and the guards, you don’t know which one is which.
With just one question/request to one of the guards, how do you find the door of Freedom?
The answer is “Please show me the door the other guard would lead me to, if I asked for the door of Freedom”. Both guards will point to the door of Death, so you take the other door.
Here’s the logic:
- The truthful guard will show you what the ying one would do – so he will point you to the Death door.
- The lying guard will show you the opposite of what the truthful one would do – the truthful guard would show you the Freedom door, so he’ll point you to the Death door instead.
Questions and answers
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?
An explorer found a silver coin marked 7 BC. He was told it was a forgery. Why?
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?
What day follows the day before yesterday if two days from now will be Sunday?
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?
Both are lying. If any of them told the truth, they would deliver one same answer.
You can’t have “Before-Christ” in the Before-Christ years, because nobody knew who this Christ was.
At the start, the number of vacant seats on the bus was x/2. After the first bus stop it becomes x/2 + y.
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.
Tom took the apple
Jim Hank, and Eddie were telling the truth
Tom and Don were lying
6. Letter-trick Brain Teasers
Letter-trick questions play with the organization, composition, and demonstration of letters to illustrate the meaning of a word or phrase.
The key to answering these questions is to examine as many aspects of the letters as possible: meaning, pronunciation, visual presentation, etc.
What does this represent: “COF FEE”?
The answer is “coffee break”.
Questions and answers
What does this mean? “GGES EGSG SEGG ESGG”
What does this mean? “ROFORKAD”
What does this mean? “CCCCCCC”
What does this mean? “F AST”
What does this mean? “GR 12” AVE”?
Get Your Free Materials Now!
Kick start your case interview practice with our Prospective Candidate Starter Pack
Over 50 tips and tricks, a framework dictionary and an example from our premium
Case Interview End-to-End Secrets Program
7. Market-sizing & Guesstimate Questions
How many ping pong balls can you fit inside a Boeing 747?
A guesstimate question asks you to estimate an obscure number; when that number represents the size of a market, it’s called a “market-sizing question”.
These questions do not require “thinking out of the box”; instead, the emphasis is placed on estimating with a structured approach. You show such an approach by breaking down the problem into smaller pieces, estimate each piece, then combine for a final answer.
This type of question is unique and popular enough among to warrant a separate guide; you should check out this article on Market-Sizing and Guesstimate Questions for deeper insights.
9. Brain Teaser Questions – Tips & Tricks
There are four tips to help you immediately improve your brain-teaser performance:
Use pen and paper
Write down both the question and your answer, and point to the note as you speak; it saves you a lot of brain power because you no longer have to recall every bit of information. Additionally, it allows you to spot unobvious details, patterns and logics. Presenting is also easy if you have such visual aids, because both you and the interviewer can easy follow the contents.
Doubt your first answer
When dealing with illusion, draw-explanation and wording brain teasers, your first instinctive answers are almost always wrong. By principle, these questions lure you into easy, seemingly correct “trap answers”. Although the approach to each type is different, you always need to be aware of those “traps”.
Draw-explanation and wording brain teasers always rely on being unconventional.
Conventions (common and accepted interpretations, methods, rules, etc.) are shortcuts to explain situations and solve problems. However, for the above brain teaser types, they will always lead you to dead-ends. So if your brain says “it’s impossible” about anything regarding those questions, immediately discard that notion – if anything, it only prevents you from reaching an answer.
Stay calm and be confident
Don’t be afraid of being “wrong”, and deliver your answer with a smile.
Brain teasers are not just about the thinking process, but also how you handle difficult situations in high-stake, high-pressure contexts. You’re supposed to remain calm and collected throughout that process; if you work through the question in a flustered, unsure manner, you’ll hurt your own chances.
Want more practice with brain teasers? There are 150 of them in the Business Intuition package of our Case Interview End-to-End Secrets Program, a comprehensive guide on every aspect of case interviews. If you’re a consulting candidate, you should definitely check that out!
Learn the Secrets to Case Interview!
Join countless other successful candidates around the world
with our Case Interview End-to-End Secrets Program!
10 example cases with 100+ real-time feedbacks on tips and techniques, 50+ exercises on business intuition and 1300+ questions for math practice!