In the competitive world of consulting, standing out from the crowd and demonstrating your problem-solving prowess is crucial to landing your dream job. Consulting firms are notorious for their challenging interviews, which often feature brainteasers designed to test your analytical thinking, creativity, and mental agility. Especially tier-2, the Big 4, boutique, and in-house consulting firm are using brainteasers in their case interviews.

These puzzles not only assess your ability to think critically under pressure but also offer a glimpse into how you approach complex problems.

To help you navigate this enigmatic world and prepare for your consulting interviews, we’ve compiled a collection of 15 engaging brainteasers that will stretch your mental muscles and hone your problem-solving skills. These carefully selected puzzles cover a wide range of topics and difficulty levels, ensuring that you’ll be well-equipped to face any challenge your interviewer may throw your way.

So, whether you’re an aspiring consultant preparing for your first round of interviews or a seasoned professional looking to sharpen your skills, dive into these mind-bending brainteasers and discover the untapped potential of your analytical mind. Happy puzzling!

The solutions are at the bottom of the page.

## Practice brainteasers

### Day of the week

If the day before yesterday was the day after Monday, what day is tomorrow?

### Water lilies

Water lilies grow in a lake, and their quantity doubles daily. It takes 48 days for the water lilies to cover the entire lake. How many days does it take for the water lilies to cover half of the lake?

### Marathon

You’re participating in a marathon race. You overtake the person in fifth place 923 meters before the finish line. What position are you in now?

### Boxes and balls

You have two boxes – one contains 50 red balls, and the other contains 50 green balls. With your eyes closed, you can draw a ball from one of the boxes. If the ball is red, you win; otherwise, you lose. To increase your chances, you can distribute the balls between the boxes however you want beforehand. How do you proceed?

### Skyscraper

Sara works on the 55th floor of a skyscraper. She often carries a pen when going up to her workplace. However, if she doesn’t have a pen, she either rides the elevator with someone or decides to get off on the 43rd floor and walk to the 55th floor. Why does she do this?

### Cost of two items

The cost of a racket and a ball together is 1.10 euros. If you know that the racket costs one euro more than the ball, how much does the ball cost?

### Smuggler

Every day, a cyclist crosses the border with a bag and smuggles something. They are always inspected, but the customs officers can never figure out what is being smuggled. What is the cyclist illicitly transporting?

### Explain a color to a blind person

How can you explain the color green to a blind person?

### Tipping

How much tip can the entire staff of a restaurant expect per day?

### Rain barrel

Two friends look into a rain barrel. One claims it is at least half full, while the other argues that it is less than half full. How can you determine who is right?

### Birthday

Max was 20 years old a week ago, but next year he will already be 23 years old. How is this possible?

### Euro coins

There are nine 1-euro coins on the dining table that all appear identical. However, one of the coins is lighter than the others. You want to determine which coin is the lightest by weighing them twice on a balance scale. How do you do it?

### Chicken and the egg

One and a half chickens lay one and a half eggs in one and a half days. How many eggs does one chicken lay in one day?

### Amazon River

Before the Amazon River was discovered, which river was the longest in the world?

### Manhole covers

Why are manhole covers round?

## Practice Solutions

### Day of the week

If the day before yesterday was the day after Monday, what day is tomorrow?

The solution to this puzzle is Friday. The day after Monday was Tuesday, which was the day before yesterday. Therefore, today is Thursday, making tomorrow Friday.

### Water lilies

Water lilies grow in a lake, and their quantity doubles daily. It takes 48 days for the water lilies to cover the entire lake. How many days does it take for the water lilies to cover half of the lake?

Since it takes 48 days for the water lilies to cover the entire lake and their quantity doubles each day, the lake must have been half-covered on the day before, which is day 47.

### Marathon

You’re participating in a marathon race. You overtake the person in fifth place 923 meters before the finish line. What position are you in now?

You are now in fifth place.

### Boxes and balls

You have two boxes – one contains 50 red balls, and the other contains 50 green balls. With your eyes closed, you can draw a ball from one of the boxes. If the ball is red, you win; otherwise, you lose. To increase your chances, you can distribute the balls between the boxes however you want beforehand. How do you proceed?

To maximize your chances of winning, follow this strategy: Since no one specified that both boxes must contain the same number of balls, put a single red ball in one box and the remaining 49 balls in the other box along with the green balls. If you pick the right box with the red ball, you’ve already won; otherwise, the chances are 50:50. Overall, this increases your winning chance to about 75%.

### Skyscraper

Sara works on the 55th floor of a skyscraper. She often carries a pen when going up to her workplace. However, if she doesn’t have a pen, she either rides the elevator with someone or decides to get off on the 43rd floor and walk to the 55th floor. Why does she do this?

The answer to this question is as follows: Sara is a short woman. Button 55, located relatively high, is too high for her to reach. If she has a pen, she can use it to reach the button. If someone else is riding the elevator, she can ask them for help. Otherwise, Sara goes to the 43rd floor, whose button she can press, and then continues on foot.

### Cost of two items

The cost of a racket and a ball together is 1.10 euros. If you know that the racket costs one euro more than the ball, how much does the ball cost?

Intuitively, you might say that the racket costs 1 euro and the ball costs 10 cents. However, that is not correct, as the price difference would be 90 cents and not 1 euro. The price of the ball is actually 5 cents, and the price of the racket is 1.05 euros, which makes the difference exactly 1 euro.

### Smuggler

Every day, a cyclist crosses the border with a bag and smuggles something. They are always inspected, but the customs officers can never figure out what is being smuggled. What is the cyclist illicitly transporting?

The most obvious answer is a bicycle. Since the cyclist smuggles something across the border every day but is never caught during inspections, it must be the bicycle itself.

### Explain a color to a blind person

How can you explain the color green to a blind person?

Blind people cannot see, so their other senses are more highly developed. These heightened senses can be used to explain the color green to a blind person, for example, through emotions, sounds, beverages, spices, or smells. Green can be described by the smell of freshly cut grass or the taste of fresh green tea.

### Tipping

How much tip can the entire staff of a restaurant expect per day?

Assuming a small restaurant, it is open for approximately 10 hours daily. The number of visitors per day depends on various factors, such as weather, location, and season. On average, you can assume about 12 restaurant visitors per hour or about 120 people per day. A person typically consumes food and drinks worth €15, so 120 times €15 = €1800. Assuming visitors tip an average of 5-10%, the entire staff can expect, at best, around €180 in tips per day.

### Rain barrel

Two friends look into a rain barrel. One claims it is at least half full, while the other argues that it is less than half full. How can you determine who is right?

To find out who is correct, the rain barrel needs to be tipped diagonally. If water pours out of the barrel before the friends can see the bottom, it was more than half full. If no water pours out, it was exactly half full. If the bottom is visible before the water flows out, it was less than half full. This method will determine which friend is right.

### Birthday

Max was 20 years old a week ago, but next year he will already be 23 years old. How is this possible?

If we assume that today is January 1st, then Max turned 20 on December 24th. Between December 25th and 31st, he must have turned 21. Therefore, Max will turn 22 later this year and will already be 23 years old next year.

### Euro coins

There are nine 1-euro coins on the dining table that all appear identical. However, one of the coins is lighter than the others. You want to determine which coin is the lightest by weighing them twice on a balance scale. How do you do it?

First, divide the coins into three groups of three. Weigh one group of three against another group of three. Two possible scenarios can occur – either the scale is balanced or not. In the first case, the lighter coin is not on the scale and is in the remaining group of three. In the second case, the lighter coin is on the higher side of the scale. In the next step, weigh the individual coins from the respective group of three against each other, following the same logic as the first weighing. Finally, check if the scale is balanced and determine which coin is the lightest.

### Chicken and the egg

One and a half chickens lay one and a half eggs in one and a half days. How many eggs does one chicken lay in one day?

Intuitively, you might immediately say that a chicken lays one egg. However, this is incorrect. If one and a half chickens lay one and a half eggs in one and a half days, then one chicken lays one egg in one and a half days. This means that in one day, a chicken lays ⅔ of an egg.

### Amazon River

Before the Amazon River was discovered, which river was the longest in the world?

Even before the Amazon River was discovered, it was still the longest river in the world – it just wasn’t known yet that this river existed and was the longest.

### Manhole covers

Why are manhole covers round?

There is more than one correct answer to this question. A significant advantage of round manhole covers is that they can be rolled, and manufacturing costs are lower. Additionally, unlike a square cover, a round cover cannot fall into the hole. This is the most crucial reason for having round manhole covers, as it significantly reduces the risk of injury.

## How Can You Practice Brainteasers?

**Introducing the Ultimate Consulting Interview Brainstorming Course: Mastering Brainteasers**

Prepare for top-tier consulting firm interviews with our comprehensive Consulting Interview Brainstorming Course, designed to make you a brainteaser-solving expert and give you the edge to secure your dream consulting role.

You can find more information about the course here.

### Course overview

This extensive program delves into various brainteaser types, covering everything from preparation strategies to tailored approaches for tackling complex problems.

### Features

- In-depth brainteaser explanation: Understand logic, patterns, and nuances of different brainteaser categories, building a strong problem-solving foundation.
- Comprehensive preparation strategies: Optimize your preparation process with effective methods that build confidence and enhance mental agility.
- Personalized problem-solving approaches: Develop customized strategies for each brainteaser type, tackling even the toughest challenges.
- 155 practice examples from simple to hard: Progressively build skills with a wide range of brainteasers, complete with detailed explanations and solutions.
- Expert tips and guidance: Benefit from seasoned instructors who share invaluable insights and advice to help you stand out in a competitive field.

By the end of this course, you’ll master the art of solving brainteasers, impress your interviewers, and pave your way to a successful consulting career.