Best Puzzle Interview Questions and Answers with Tips

In today’s job market, it is important to not only showcase technical skills but also demonstrate critical thinking and problem-solving abilities. This has led to the rise of puzzle interview questions. 

These interview questions have become a common part of job interviews and the hiring process, especially in fields such as software development and data science. They allow employers to assess your critical thinking skills and problem-solving abilities. This guide will explore the realm of puzzle interview questions and answers, providing tips on how to tackle them successfully and offering sample questions and answers for practice. 

Whether you are an experienced professional or a beginner, mastering these types of questions can greatly improve your chances of excelling in interviews and securing your dream job.

What Comes to Mind When You Hear of Puzzles for Interview?

Puzzle interview questions are challenges that require candidates to use their critical thinking and logical reasoning skills to find a solution. These problems help interviewers assess a candidate’s problem-solving abilities, analytical skills, and thought process. They are commonly used in interviews for software development, data science, or engineering roles as they demonstrate one’s ability to solve complex problems using high-order thinking strategies. While not directly related to the job role itself, practicing these types of puzzles can improve your chances of answering correctly during an interview and impress the interviewer with your problem-solving skills.

How to Answer Puzzle Questions?

Puzzle questions can be a fun and challenging part of interviews. Here’s a concise guide on how to solve them effectively:

• Break It Down: Breaking the puzzle into smaller, more manageable parts allows for a systematic approach to problem-solving. Addressing each component individually simplifies the overall problem and makes it easier to find solutions.
• Look for Patterns: Identifying any recurring patterns or sequences within the puzzle can provide valuable insights into potential solutions. Recognizing patterns often leads to quicker problem-solving and helps uncover hidden clues.
• Use Logical Reasoning: Applying deductive and inductive reasoning helps in analyzing different aspects of the puzzle. By considering various scenarios and eliminating impossibilities, logical reasoning narrows down the range of possible solutions.
• Think Outside the Box: Being open to unconventional solutions encourages creativity and innovation in problem-solving. Sometimes, the answer lies in thinking beyond conventional methods and exploring alternative approaches.
• Stay Calm and Patient: Maintaining composure and patience is crucial, especially when faced with challenging puzzles. Avoiding rushing allows for clear thinking and thorough analysis, increasing the likelihood of finding the correct solution.
• Practice Regularly: Regularly engaging in puzzle-solving activities improves problem-solving skills over time. Practicing with different types of puzzles enhances familiarity and adaptability, making it easier to tackle new challenges effectively.

Puzzle Questions with Answers for Interview

Here are some sample puzzle interview questions and answers that you might encounter in an interview:

Q1. How can you accurately measure 45 minutes using two ropes that take one hour to burn from end to end, but do not burn at a consistent rate?

Answer: Here’s how you can answer this question:

• Light both ends of the first rope and one end of the second rope simultaneously. 
• It will take 30 minutes for both ends of the first rope to burn completely, while one end of the second rope is also burning. (This means that 30 minutes more of the second rope is remaining for you to burn. Right?) 
• At this point, Start burning the other end of the second rope. 
• Now, instead of letting it burn out for 30 more minutes from one end, you’ve been able to reduce the burn time to 15 minutes. 
• Once this is done burning, 15 minutes would have elapsed. Plus the initial 30 minutes, we have accurately measured 45 minutes. 

Q2. Two trains, each traveling at a speed of 40km/h, are heading towards each other from a distance of 80km. A bird is flying back and forth between the two trains at a constant speed of 100km/h until they collide. How many kilometers does the bird cover in total during this time?

Answer: We are given that two trains are running towards each other at a speed of 40 km/h. Now, a bird is flying from one train to the other at a speed of 100 km/h. Since this is higher than the relative speed of the trains (which is calculated by adding their speeds), it can easily fly back and forth between them without being caught in any collisions.

To find out how much distance it covers during its flight time, we need to determine when exactly these trains will collide. To do so, we use the formula: 

Time = Distance / Relative Speed.

Time = 80 km / 80 km/h = 1 hour

So, the bird will keep flying for 1 hour. In that time, it will cover a distance of

Distance = Speed × Time = 100 km/h × 1 hour = 100 km

Therefore, the bird will have covered a total distance of 100 kilometers before the trains collide.

Q3. How can you measure one litre of water using a seven-litre and three-litre container? 

Answer: This is one of the logical puzzles for an interview and the answer is: “I will fill the 7-litre container with water. Then I will pour the water into the 3-litre container. I should have 4 liters of water left. Again, I will pour out the 3-litre container and fill it up with water from the remaining 4 litres. Now, I should have 1 liter of water left in my 7-liter container”. 

Also Read: Problem Solving Interview Questions.

Q4. There are three switches in one room and you need to figure out which one controls a fan in another room with the least amount of trips into that other room.

Answer: Turn on one switch and wait for a few minutes to allow enough time for it to run. After a few minutes, turn off this first switch. Then turn on the second switch and immediately go to observe the fan in another room. Now there are three different scenarios that can occur:

• If you find that the fan is still running, then it means that Switch 2 (which you just recently turned on) controls the power supply to the fan. This means that you have successfully identified the control switch for the fan.
• If you find the blades of the fan are spinning slowly or there is a slight humming sound coming from it, then it indicates that Switch 1 controls the power supply to the fan and not Switch 2. 
• However, if after turning on both switches the fan is still not moving, this means that neither switch 1 nor 2 is the right switch. Instead, It’s switch 3. (The one you didn’t switch on). 

Q5. How many races would you need to hold to determine the four fastest cars out of 36 on a six-lane car track?

Answer: To answer this puzzle question, think of the solution in this manner: 

1. Divide the 36 Cars into Six Groups:

• Group A: Cars 1 to 6
• Group B: Cars 7 to 12
• Group C: Cars13 to 18 
• Group D: Cars 19 to 24 
• Group E: Cars 25 to 30
• Group F: Cars 31 to 36

2. Conduct Six Races: Race 1 includes cars from group A. The winner of this race is the fastest car in group A. Repeat for each remaining five groups of cars, determining a winner for each. After conducting all six individual races, you will have determined one winner per group (six total). These winners are

• Winner of Race 1 – Fastest car in Group A
• Winner of Race 2 – Fastest car in Group B
• Winner of Race 3 – Fastest car in Group C  
• Winner of Race 4 – Fastest car in Group D  
• Winner of Race 5 – Fastest car in Group E
• Winner of Race 6 – Fastest car in Group F

3. Conduct One Final Race (Race 7) With the Six Winners:

To determine which of these initial six winning cars is truly the fastest, you’ll need to conduct another race that includes all of them. The first 4 winners of this seventh and last race are the 4 fastest cars. The winner of this final race becomes:

• The overall winner
• Runner-up (second-place finisher)
• Third place finisher 
• Fourth-place finisher

By following these steps, you can find the fastest four cars out of the initial 36 by conducting a total of 7 races.

Q6. Three ants are sitting on each corner of a triangle. These ants randomly select a direction and begin moving along the edge of the triangle. What is the probability that any two ants collide?

Answer: The answer to the above question is: 

• Let us assume the ants are moving randomly along the edges of the corner they are sitting in. In this situation, they have two choices to move, either clockwise or counterclockwise. 
• To calculate the collision probability, think of possible ways they move without colliding. 
• Each ant has two choices for their first move, and for each of those choices, there are two choices for the second move, and so on. So, there are 23 = 8 possible ways the ants can move. 
• Out of the eight ways, only two do not cause a collision when all the ants move in a clockwise or counterclockwise direction. So, the probability of collision is 6/8.

Q7. Four people are trying to cross a bridge at night. They have only one flashlight and every person needs it to cross the bridge. Only two people can cross the bridge at the same time. Given that every person will take a different amount of time to cross the bridge: 1 minute, 2 minutes, 7 minutes, and 10 minutes, what is the shortest possible time for all four of them to cross the bridge?

Answer: You can answer the question in the following way: 

• Let us assume the four people – A, B, C, and D, take 1 minute, 2 minutes, 7 minutes, and 10 minutes respectively, to cross the bridge. 
• When two people move together, they have to move at a slower person’s speed. So, the fastest two people (A and B) will cross the bridge first. This will take 2 minutes. Now, one of them (A) comes back with the flashlight because the bridge cannot be crossed without one. 
• Next, the slowest two people (C and D) will cross the bridge together. This will take them 10 minutes. B will now come back with the flashlight. 
• A and B will cross the bridge together again in 2 minutes. 
• Now, the total time taken by then will be 2 + 10 + 2 = 14 minutes. This is the shortest possible time for all four of them to cross the bridge.

Q8. There are 25 horses and five race tracks. Find the fastest three horses among the 25 in the least number of races.

Answer: You can answer the question in the following way: 

• First, group the horses into groups of five and race each group. We will have five races. 
• Let us assume there are five groups, A, B, C, D, and E, and the winner of each race is the fifth horse in the group. So, we will have A5, B5, C5, D5, and E5 as the winners. 
• Subsequently, assume the fourth horse in each group came second, the third horse came third, the second horse came fourth, and the first horse was the last in the race. 
• Now, we will race the winners i.e. A5, B5, C5, D5, and E5. Let us say A5 won the race, B5 came second, and C5 came third. 
• We have A5 as the fastest horse of the entire 25 lot. Now, for the second position, we have B5 and A4. For the third position, we have C5, B4, or A3. 
• Therefore, we race these five horses. The horses that come first and second in this race are second and third fastest in the entire group. 
• So, the minimum number of races required to find out the first, second, and third fastest horse in the entire group is 7.

Q9. The time in an analog clock is 3:15. What is the angle between the minute hand and the hour hand?

Answer: This is how you can solve the puzzle:

• We will use the following formulas:
  • Angle made by hour hand (H) from 12 o’clock = (30 * hour) + (0.5 * minutes)
  • Angle made by minute hand (M) from 12 o’clock = (6 * minutes)
• Now, we have H = 3 and M = 15. So, according to the above formula, we will have:
  • Angle made by hour hand (H) = (30 * 3) + (0.5 * 15) = 90 + 7.5 = 97.5 degrees
  • Angle made by minute hand (M) = (6 * 15) = 90 degrees
• The angle between the minute hand and the hour hand is the difference between these two angles. So, 97.5 – 90 = 7.5 degrees.
• At 3:15, the angle between the minute hand and the hour hand of an analog clock is 7.5 degrees.

Q10. There are 9 balls, and one of them has a weight flaw. What will be the fewest amount of comparisons to determine the defective ball?

Answer: Note that it is not specified if the weight flaw has made the ball heavier or lighter. So, we will divide the 9 balls into three groups of 3 balls each. Each of these groups will require two comparisons to determine if the ball is heavier or lighter. Now, divide the three balls into three groups of one, each requiring one comparison. Therefore, just three comparisons are required.

Q11. Assume there is a 100 x 100-meter pond with a diamond in the middle of the pond over a large stone. You have two 48-meter planks and must remove the diamond from the pool using them. How will you get the diamond out of the pond?

Answer: You can solve this problem in the following way: 

• Let the side length of the square pond be 100 meters, with one side on the positive X-axis and the other side on the positive Y-axis. 
• Next, place one plank on the line segment connecting (33,0) and (0,33). Using the Pythagorean theorem, we get the line segment length as 46.669048. This allows you to balance the plank on both sides of the pond.
• Now, place the other plank on the line segment connecting the midpoint of the previous first plank and the center of the big stone which is also the center of the river.
• The length of this line segment is 47.5 meters. With both planks positioned securely, you can now get the diamond out of the pond.

Q12. You have two sandglasses, one measures 4 minutes and the other 7 minutes. How can you measure exactly 9 minutes?

Answer: You can solve this problem in the following way: 

• Start both sandglasses at the same time.
• When the 4-minute sandglass runs out, turn it over.
• When the 7-minute sandglass runs out, turn it over.
• When the 4-minute sandglass runs out again (8 minutes in total), turn it over once more.
• The sandglass will now measure 1 minute, totaling 9 minutes.

Q13. Imagine you have twelve identical-looking squares and one of them is slightly heavier than the rest. You have a two-pan balance scale but can only use it three times to determine which square is the heaviest. How can you find the heavier square?

Answer: You can solve this problem in the following way: 

First, divide the twelve squares into three groups of four squares each. Weigh any two groups against each other. If they balance, then the heavier square is in the third group. If one side is heavier, then the heavier square is in that group.

Now you have narrowed down the heavier group to four squares. Take these four squares and weigh two of the four squares against each other. If they balance, then the heavier square is one of the two squares that are not weighed. If one side is heavier, then the heavier square is on that side.

Now you have narrowed down the search to two squares. Take these two squares, and weigh one against the other, whichever is heavier is the one you’re looking for.

Q14. You have a 7-liter tub and a 4-liter tub, and there are no markings on either tub. You need to measure exactly 5 liters of water using only these two tubs. How can you do it?

Answer: You can solve this problem in the following way: 

• Start by filling the 4-liter tub to the top.
• Pour the water from the 4-liter tub into the 7-liter tub.
• Now, you have 4 liters of water in the 7-liter tub, leaving 3 liters of space.
• Refill the 4-liter tub to the top again.
• Pour the water from the 4-liter tub into the 7-liter tub until it is full. This will fill up the 7-liter tub, leaving 1 liter of space in the 4-liter tub.
• Now, you have exactly 1 liter of water in the 4-liter tub.
• Empty the 7-liter tub.
• Pour the 1 liter of water from the 4-liter tub into the empty 7-liter tub.
• Refill the 4-liter tub to the top one more time.
• Pour the water from the 4-liter tub into the 7-liter tub until it is full.
• Now, the 7-liter tub contains 5 liters of water.

Q15. There is a river that needs to be crossed using a boat. The boat can carry only two people at a time. A group of four people have to cross the river: Adam, Bill, Charlie, and David. Adam takes 1 minute to cross, Bill takes 2 minutes, Charlie takes 7 minutes, and David takes 10 minutes. What is the shortest time in which all four can cross the river?

Answer: You can solve this problem in the following way: 

• Adam and Bill cross the river (2 minutes).
• Adam returns (1 minute).
• Charlie and David cross the river (10 minutes).
• Bill returns (2 minutes).
• Adam and Bill cross the river again (2 minutes).
• Total time: 2 + 1 + 10 + 2 + 2 = 17 minutes.

Tips & Tricks to Correctly Answer Puzzle Interview Questions 

Solving puzzles asked in an interview can be tough, but if you approach them correctly, you can impress your interviewer by demonstrating your ability to solve problems and think outside the box. Here are some tips on how to answer puzzles for interviews effectively:

1. Stay Calm & Think: Stay calm and keep it together. Think about the puzzle and what type of puzzle it is. Break it down into smaller parts and use different methods to solve each part until you find the answer.
2. Ask Questions to Clarify:  Always ask for clarification from the interviewer if needed to establish a common understanding and gather all information. 
3. Use Logical Strategies: Try different ways of solving questions and get rid of the wrong options. If there is a picture or drawing involved, try making your diagram or sketch to help you understand the problem better.
4. Think Creatively & Outside The Box: Always explore new possibilities that may seem unconventional at first. Sometimes, the best solutions are not what everyone else is doing. 
5. Explain your Thought Process and Answers: Explain how you would solve the important puzzles for an interview and talk about your thoughts as you work through it. This shows that you can handle difficult situations and think critically.
6. Give an Answer: Sometimes interviews are not looking for the right answer, but rather how you approach and solve problems. Therefore, it is important to always provide an answer, even if you’re not sure it’s right.
7. Stay Positive & Learn From Your Mistakes: Keep a good attitude during the interview, even when dealing with difficult top puzzles for interviews. If you make a mistake, use it as an opportunity to learn and think about how you would handle similar challenges differently in the future.

Also Read: Top Interview Tips.

Conclusion

Puzzle interview questions are useful in evaluating a candidate’s problem-solving, critical thinking, and analytical abilities. To handle these challenges well, it is important to follow the tips we’ve provided. It is also crucial to always provide an answer even if unsure. We’ve provided various interview puzzles with answers to help you showcase your skills. 

Have you ever been faced with a puzzle question during an interview? Tell us in the comment section how you dealt with it. Also, read about how to answer interview questions confidently.

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