## Introduction

Mathematics has always been a subject that requires a lot of practice, and what better way to stimulate your brain than with math riddles? Riddles are a fun way to challenge your mind and improve your problem-solving skills. That's why math riddle books are so popular among students and math enthusiasts. However, some of the most intriguing riddles are often left unanswered. In this article, we will reveal the answer key to some of the most popular math riddles books never written.

## The Missing Dollar Riddle

The missing dollar riddle is a classic example of a math riddle that has puzzled people for years. The riddle goes like this: Three friends go to a restaurant and decide to split the bill equally. The bill comes to $30, so each person contributes $10. However, the waiter realizes that he made a mistake and the actual amount should have been $25. So, he gives the friends back $5. But the friends cannot split $5 equally, so they decide to each take $1 and leave the remaining $2 as a tip. Now, each friend has paid $9, which totals $27, and the waiter has $2. But $27 + $2 = $29. Where is the missing dollar? The answer to this riddle is actually very simple. The friends have paid a total of $27, which is the correct amount. The $2 tip should not be added to the total, as it is not part of the original bill. So, there is no missing dollar.

## The Monty Hall Problem

The Monty Hall problem is another famous math riddle that has baffled people for years. The riddle goes like this: You are a contestant on a game show, and there are three doors. Behind one door is a car, and behind the other two doors are goats. You choose a door, but before it is opened, the host, who knows what is behind each door, opens one of the other doors to reveal a goat. He then asks if you want to switch your choice to the remaining door. Should you switch? The answer to this riddle is yes, you should switch. Switching your choice gives you a 2/3 chance of winning the car, while sticking with your original choice only gives you a 1/3 chance. This is because when you first chose a door, you had a 1/3 chance of being correct, but the host's decision to open one of the other doors and reveal a goat changed the odds in your favor.

## The Two Envelope Problem

The two envelope problem is a math riddle that involves probability and decision-making. The riddle goes like this: You are given two envelopes, each containing money. One envelope has twice as much money as the other. You are allowed to choose one envelope and keep the money inside. After you have made your choice, the person who gave you the envelopes offers you the chance to switch. Should you switch? The answer to this riddle is that it does not matter if you switch or not. If you choose the envelope with less money, switching will give you more money. If you choose the envelope with more money, switching will give you less money. So, it is a matter of personal preference.

## Conclusion

Math riddles are a great way to exercise your brain and improve your problem-solving skills. However, sometimes the answer to a riddle can be elusive. We hope that this article has provided you with the answer key to some of the most popular math riddles books never written. Remember to keep challenging yourself and never stop learning.

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