10 Tricky Puzzles That Stump People in Job Interviews (And How to Solve Them)

Picture this – you walk into a job interview feeling confident and prepared. You‘ve researched the company, practiced your answers to common questions, and polished your resume until it shines. But then the interviewer throws out a puzzle and says "If you can solve this, you might just get the job." Your heart starts racing as you stare at the seemingly impossible riddle in front of you.

Sound familiar? Brainteasers and logic puzzles have become increasingly common in job interviews, especially for highly analytical roles like software engineering, management consulting, and data science. While they may seem daunting at first glance, most interview puzzles actually have surprisingly simple solutions. The key is to stay calm and approach them critically and logically.

Interviewers use tricky puzzles to evaluate candidates‘ problem-solving skills, creativity, and ability to think on their feet. They want to see how you tackle a challenge you‘ve likely never seen before. What‘s your thought process? Do you make smart assumptions? Can you break a complex problem into more manageable parts?

When you encounter a puzzle in an interview, resist the urge to panic if the answer isn‘t immediately apparent. Take a deep breath and start thinking it through step-by-step. Talk through your reasoning out loud so the interviewer can see the gears turning. And if you get stuck, don‘t be afraid to ask clarifying questions or propose several potential solutions. Often, putting forth a clever approach is just as important as finding the right answer.

To help you sharpen your puzzle-solving skills, we‘ve compiled a list of 10 of the trickiest puzzles frequently asked in job interviews. We‘ll walk through the problem and explanation for each so you can build your logical thinking abilities and arrive at your next interview ready to impress. Let‘s dive in!

Puzzle 1 – Who Took the Coconut?

Ten people are stranded on a deserted island with a large pile of coconuts and a monkey. They decide to split the coconuts evenly between them and any remaining will go to the monkey. One person then proposes that they split the coconuts the next morning, so that each would have a chance to take some without the others knowing.

That night, the first person takes 1/10th of the coconuts and hides them. On his way back to camp, he trips over a coconut. He doesn‘t want to go back to the hiding spot, so he throws it to the monkey.

Later, the second person wakes up and does the same. He takes 1/10th of the remaining coconuts, and again finds one extra, so he throws it to the monkey. And so on.

In the morning, the group divides the remaining coconuts between them. Since each had taken approximately the same amount, they could divide the pile evenly, but had one remaining coconut. They gave this to the monkey as well.

What is the smallest number of coconuts that they could have started with?

Answer: 3121 coconuts

Explanation:

• If they started with 3,121 coconuts, each person would take 312 coconuts, except the last, who would take 313.
• The first 9 people would find one coconut left over when taking their share (as 3121 is divisible by 10 but leaves a remainder of 1). They would throw this extra coconut to the monkey.
• When the last person takes their share, they take 313 coconuts, leaving none behind.
• In the morning, 312 coconuts are left to divide among the 10 people. This is evenly divisible, with 31 coconuts each and one left for the monkey.

The key to this puzzle is working backwards. Let‘s call the initial number of coconuts X.

The last person will find X/10 = a whole number, so X must be divisible by 10.

The 9th person will find (X-X/10)/9 = a whole number, so X-X/10 must be divisible by 9. And so on, down to the 1st person.

Therefore, X-X/10 must be divisible by 2-9, and X itself divisible by 10. The smallest X that satisfies all these conditions is 3121. You can find this by computing the least common multiple of the numbers 1-10.

Puzzle 2 – The Three Hat Colors

Three smart logicians are told they will be given colored hats from a group of five hats: two are black and three are white. The logicians will be blindfolded and will not be able to see or feel the color of their hat but will be able to see the hats worn by the two others.

The blindfolds are removed and the logicians take a look at each other. The first logician is asked if he knows the color of his hat, to which he replies "No." The second logician is asked if he knows the color of his hat, to which he also replies "No." Finally, the third logician is asked if he knows the color of his hat, to which he replies "Yes."

What color hat is the third logician wearing and how does he know?

Answer: White

Explanation:
The third logician reasons this way:

Suppose I was wearing a black hat. The first logician saw either one black and one white hat (if the second was wearing white) or two white hats (if the second was wearing white).

If the second logician saw a black hat on me and a white hat on the first logician, he would have known his own hat color was white based on the first logician‘s answer. But he said he didn‘t know. So he must have seen either two black hats or two white hats.

But the first logician didn‘t know his hat color either, which means he saw one black and one white hat. Therefore, I must be wearing a white hat.

Puzzle 3 – Defective Ball Weighings

You have 8 balls that all look identical. However, you know that one is defective and weighs slightly less than the others. Using a balance scale only twice, how can you determine which ball is defective?

Answer:
First weighing: Put 3 balls on each side of the scale. If one side is lower, the defective ball is in that group. If they balance, the defective ball is one of the remaining two.

Second weighing: From the group of 3 that is lighter (or from the remaining 2 if the first weighing balanced), put 1 ball on each side of the scale. If one side drops, that ball is defective. If they balance, the remaining ball not weighed is defective.

Explanation:
This puzzle exploits the fact that 8 = 3 + 3 + 2. We have just enough weighings to divide the balls into three distinct groups and locate the defective ball.

After the first weighing, we will have either narrowed it down to a group of 3 balls (if one side was lighter) or 2 balls (if both sides balanced).

With one more weighing, we can definitively identify the defective ball from either of those scenarios. If we had started with 7 or 9 balls, we wouldn‘t have had quite enough information after two weighings to be sure.

Tips for Solving Interview Brainteasers

Feeling stumped? Here are a few strategies to try when a tricky puzzle has you flummoxed:

1. Pause and don‘t panic. It‘s normal to not see the answer right away. Take a deep breath and start considering the information you have.

2. Break the problem into smaller parts. Tackle just one element at a time until you can start piecing together a solution.

3. Consider different perspectives. Is there another way to represent or visualize the problem? Would working backwards help?

4. Watch out for assumptions. Your brain often makes intuitive leaps and takes things for granted. Make sure you‘re working with only the information given.

5. Explain your reasoning out loud. This helps the interviewer understand your thought process and see that you have strong problem-solving skills even if you don‘t land on the right answer.

6. Practice! The more puzzles you encounter, the easier it will be to recognize patterns and common problem-solving techniques. Websites like BrainBashers and Brilliant offer great collections to strengthen your skills.

Remember, interviewers aren‘t trying to trick you. They genuinely want to see how you think. Trust your intelligence and don‘t be afraid to get creative. With the right mindset and a bit of practice, you‘ll be solving even the toughest interview puzzles with confidence and flair.

Your turn! What‘s the trickiest puzzle you‘ve ever encountered in an interview? How did you approach solving it? Share your experiences and favorite brainteasers in the comments.