How to Solve a Brain Teaser in a Job Interview
You might be more familiar with seeing brain teasers in the end pages of a newspaper, but some industries also use them as part of the interview process. But what are brainteasers for in job interviews and how can you solve them?
We’ll explain the 1) purpose of brain teasers and provide you some of the 2) most common teasers used in job interviews. We’ll also give you tips on 3) how to prepare for a job interview and 4) the three-step approach you should use to solve a teaser.
WHAT IS A BRAIN TEASER?
Brainteasers are not a new invention, as we humans have been interested in puzzles for a long time. In fact, one of the earliest brainteaser enthusiasts was Greek mathematician Archimedes, who used to devise mathematical problems for his fellow citizens to solve.
So, what are these brainteasers? The Cambridge dictionary definition states brainteasers to be “a problem for which it is hard to find an answer, especially one which people enjoy trying to solve as a game”.
Brainteasers are therefore types of puzzles and they require plenty of thought to answer. Typically, brainteasers require quite a bit of out-of-the-box thinking. The answer is not an easy one to find, but the person must use lateral thinking and intuitiveness.
The focus of a brainteaser is usually on a puzzle or a specific problem. This excludes many other types of questions, which might be challenging, but won’t count as a brainteaser. This includes things such as:
- Tough technical questions
- Value based questions
- Failure or weakness based questions
While these might be challenging questions, they aren’t brainteasers.
Brainteasers are typically found in newspapers and magazines, as something fun for the reader. But they’ve also found their way into the world of job interviews. The popularity of brainteasers depends a little about the industry, as well as the country. Nonetheless, it is a good idea to understand brainteasers, in case you ever find yourself in a situation where you’re presented with a brainteaser.
Let’s start by looking at some simpler brain teasers.
We’ll explore the use of brainteasers in job interviews in more detail below, but it’s now time to look at some examples of commonly used brainteasers.
When it comes to brainteasers in job interviews, the questions often fall under two categories: questions with correct answers and questions with no correct answer.
Questions with a correct answer
Questions with correct answers are often math questions. Therefore, they are typically used in technical and finance industries, which require good mathematical skills and logical thinking.
Below are a few examples of these types of brainteasers. While the wording or the examples used may not be the same, the examples provide the most common type of brainteasers you could expect. We’ve included the answers to these questions, but try to guess the answer first before checking!
Example brainteaser 1: You roll two fair dice, what is the probability that the sum is 9?
Example brainteaser 2: If time is 3:15, what is the angle between the hour hand and the minute hand on a clock?
Example brainteaser 3: You’re in a room with three light switches, each of which controls one of three light bulbs in the next room. Your task is to determine which switch controls which bulb. All lights are initially off, and you can’t see in one room from the other. You may inspect the room only once. How can you know which switch is connected to which light bulb?
Example brainteaser 4: What can you hold without ever touching, or using your hands?
Answers to the brainteasers
Brainteaser 1: The possible pairs of dice are: 3+6, 4+5, 5+4 and 6+3. Probability is therefore 4/36=11%.
Brainteaser 2: 7.5 degrees. The hour hand moves around every 12 hours, which is 360 degrees in 12 hours or 30 degrees per hour. At 3, the hour hand points exactly at 3. This means that 15 minutes later, the minute hand is pointing at 3 and the hour hand is pointing 7.5 degrees past it.
Brainteaser 3: Assign the switches with numbers 1, 2 and 3. Leave switch 1 off. Turn the second switch on for five minutes and turn it off. Turn switch 3 on and leave it on. Enter the room. The bulb currently on is controlled by switch 3. Feel the other bulbs for heat. The bulb, which is off, and warm is controlled by switch 2. The cold bulb is switch 1.
Brainteaser 4: Your breath.
Questions with no single correct answer
But job interviews often aren’t about testing your math skills, but are more focused on your logical thinking and creativity. This is why they often tend to use brainteasers with no correct answer.
These are designed to find more about your approach to solving a problem and your ability to think on your feet. These brainteasers are not as much about the answer you give, but the way you go about solving them.
There are two types of questions with no correct answers: the questions with a logical solution and often a possible correct answer, and the questions that aren’t possible to solve in any sensible way, but aim for a creative answer.
Check out these hard to solve brain teasers and how to solve them.
Again, we’ve added some common brainteaser examples, which are popular in job interviews. We’ve also included a few ways you could answer these questions.
Example brainteaser 1: If you had 5,623 participants in a tournament, how many games would you need to be played to determine the winner?
Example brainteaser 2: How many quarters of pizza do Americans eat a month?
Example brainteaser 3: How many footballs can fit inside a Boeing 747?
Example brainteaser 4: How would you move Mount Fiji?
Example brainteaser 5: Why are manhole covers round?
Answers to the brainteaser
As you probably noticed, questions 1 to 3 can be answered with a near correct answer. In fact, if you had access to the required data, it would be possible to answer the questions correctly. But in a job interview, the focus is more on estimates and whether you take all the different aspects of the questions into account.
Below answers are therefore focused on the averages and the focus is on the things you should consider when giving the answer.
Answer 1: There are potentially an unlimited number of answers to this brainteaser. The point here is to ask questions. Questions you need to ask to solve the brainteaser include:
- Are the participants individual competitors or members of bigger teams?
- If teams, what is the number of teams?
- What is the tournament structure? Single elimination rounds or do each team get to play a specific number of games?
Answer 2: To answer this question, you need to have an estimate of the population of the US, make a guesstimate on how many people eat pizza. After that guesstimate how many slices a person would eat and how often in a month. Then you can calculate the average size of a pizza.
For instance, the figures could look something like:
- Population around 300 million
- Two out of three eat pizza -> 200 million eat pizza.
- Average person eats two slices of pizza twice a month, meaning four a month.
- The average slice is six inches at the base and ten inches long -> 30 square inch -> four slices is 120 square inches.
- One square foot equals 144 square inches and on average one person would eat around one square foot per month, if you round up the answer.
- 200 million times one square foot = 200 million square feet of pizza a month.
Answer 3: You’ll need to consider the size of a Boeing 747 and the size of an average football. Boeing 747 has a passenger volume of around 876 cubic meters, with cargo volume of 159 cubic meters. The average football is 22 inches in diameter. The average would therefore be around 47,000 balls.
Since the focus is not on the correct answer, you should consider asking extra questions. For example, are they talking about football (soccer) balls or American footballs? Can you use the fuel tank and does the airplane have seats attached?
The final two brainteasers, on the other hand, don’t have an actual answer. For example, moving Mount Fiji from one spot to another isn’t really a logical question, as you wouldn’t be able to do so. The idea is, therefore, to focus on how you approach the question and how good you are thinking outside of the box.
Answer 4: The questions, popularized by Microsoft according to reports, can be answered in a numerous different ways. Here are some of the possible solutions:
- Mount Fiji is already constantly moving, as the Earth is rotating around its axis.
- You could create a massive earthquake, which could shift the mountain.
- Take a picture of it and carry the image elsewhere.
- Take a piece of the mountain from the right and add it on the left. This would continue to move the mountain.
Answer 5: This is another out-of-the-box kind of questions. The possible answers could include:
- Because manholes are round and any other shape wouldn’t fit it.
- A round manhole cover is easier to move, as it can be rolled.
- Circular covers are easier to place on the opening, since they don’t require precise aligning.
Some further examples of brain teasers and how to solve them.
WHY DO INTERVIEWS USE BRAINTEASERS?
Whilst we can agree that brainteasers are a fun way to spend a few minutes (or hours!), but what is the reason behind job interviews using them.
As mentioned above, the idea behind brainteasers in an interview isn’t about finding the correct answer, but more about the journey to an answer.
In fact, the candidate’s ability to answer a brainteaser (right or wrong) can reveal more information to the interviewer and help the interviewer understand whether the person is the right fit for the role.
Brainteasers generally help the interviewer to analyze the candidate’s proficiency in:
- Problem solving – How fast can you analyze the problem in question and come up with a possible solution?
- Critical thinking–Are you able to see the big picture and evaluate all the different options and aspects behind the question?
- Analytical skills – What is your ability to analyze different pieces of data and use them to determine probability? Are you able to make calculations based on the information you have available?
- Creativity and out-of-the-box thinking – Can you take an innovative approach to problems? Can you see past the ‘obvious’ solutions and surprise the interviewer with a fresh approach?
- Their ability to think on their feet – Are you able to come up with a solution even when you haven’t been able to prepare for it?
- Their ability to perform under pressure – Will you be able to remain calm and composed even when you’re presented a tricky brainteaser?
When faced with a brainteaser, you should always remember the focus is not so much on the actual answer, but the way you approach the problem.
Jean Eisel, director of the Career Management Center at Duke’s Fuqua School of Business, told Monster, “You don’t necessarily have enough information to give the answer. They’re (interviewers) really looking at how people process information”.
HOW TO PREPARE FOR BRAINTEASERS?
Since job interviews don’t always follow a similar pattern, it’s impossible to know whether you have to answer a brainteaser or not. Your interview success won’t be determined by how well you answer a single brainteaser, so don’t make it the central focus of your interview preparation.
Nonetheless, it can be helpful to understand some of these basics beforehand, as you’ll be more able to stay calm and composed in case a brainteaser comes up. The focus of your preparation should be on understanding what brainteasers are, what the interviewer is trying to measure with it and how you can go about solving them.
Go through the examples above to understand the different kind of brainteasers. You can find further brainteasers online and even watch the video below for some common brainteasers.
HOW TO APPROACH A BRAINTEASER?
The final part of your preparation and understanding of brainteasers should involve the right approach to solving the problem. There are three steps to approaching and solving a brainteaser and you should use this tactic in a job interview.
Step 1: Take a moment to understand the question
First, if the interview asks you a brainteaser, stay calm and take a deep breath. Don’t blurt out the first thing that comes to your mind. A good trick is to repeat the teaser aloud while you gather your thoughts and analyze the kind of question you are presented with.
Think whether the problem has a single solution or is it a more open-ended question. What are the interviewers looking for with the question?
For example, if the problem is a simple math question, you can start working on the solution. On the other hand, if it seems like a creativity question, such as the Mount Fiji, one, start thinking a fun and innovative answer.
Step 2: Clarify any issues you might have
Don’t be afraid to ask questions. In fact, it’s going to tell the interviewer a better ability to solve problems and be analytical if you do. Follow-ups also give you a little more time to think and gather your thoughts.
It is often possible to use pen and paper to make notes. You can also use them to draw graphs and to visualize your answer and approach. This can show the interviewer your ability to analyze and think about the big picture.
Step 3: Explain your thinking process
Finally, you should explain your thinking process behind the answer, not simply blurt it out. You can present your abilities to solving complex problems, as well as highlight your creativity, by talking through your thinking process and the approach you took.
For example, on the Boeing 747 question, you don’t want to simply answer with the final estimate. Instead, go through the different sets of data you need to know, the way you reached to your estimates and how you then calculated the final answer.
If you had no idea of the size of a football, you should explain what estimate you used. For instance, you could say that you assume a football is slightly smaller than basketball, which you play and therefore, you estimated the ball to be about 22 inch.
Remember, the focus should be on your thinking process and logical thinking skills, not whether or not you used the exact data or numbers. Even in the questions with a single correct answer, you can salvage points by highlighting the approach you’d take and the honesty of winging it if all else fails.
Brainteasers are not the most common part of today’s job interviews, but certain companies still regularly use them. It can therefore be helpful to understand why you might come across them and the approach you should take to solve them.
You shouldn’t ever stress about brainteasers too much – they are more about analyzing your creative and problem solving skill than a correct answer. Always keep a cool head and focus on explaining your approach and the thinking behind your answer.
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