Zack Guido - Of Course!: The Greatest Collection of Riddles & Brain Teasers For Expanding Your Mind

Of Course! The Greatest Collection Of Riddles & Brainteasers For Expanding Your Mind

By Zack Guido

Copyright 2013 by Zack Guido

Dedicated to the open-minded, the gifted, and the forward-moving.

Table of Contents

Of Course! - An Introduction

This book is the result of a lifelong obsession with riddles and brain teasers. It is a selection of the best riddles that I have come across in my many years of collecting them. I started with hundreds of problems of all types and managed to whittle it down into a very refined collection. These problems are designed to make you problem solve in ways you may not be used to, challenge the way you think, and afford you with the great feeling of that of course! moment of clarity. In selecting the riddles for this collection I opted for ones with elegance, single solutions, fun lines of thought, and convention-twisting logic. I tried to avoid repeats; each riddle should have something unique about the way you need to solve it. I also tried to avoid anything involving complicated mathematics; there should be no riddle here that requires a calculator or a formal education in math or physics. Though I will admit to you there are a handful of problems that do involve a little math, but they are such good brainteasers that they just had to be included! There are also no riddles that require any factual knowledge or an above-average vocabulary. Finally, there is absolutely no wordplay! Though it is hard to determine how difficult a riddle is, they are sequenced in the book in an intentional order to be more and more satisfying for the reader as they make progress. There may be some problems that you will find unappealing or unfulfilling, but that is to be expected with a collection of this size and diversity. I expect that at the very least there are no riddles where the solution feels completely unsatisfying.

My hope is that in reading this and thinking through these riddles you will enjoy yourself, feel a sense of accomplishment, learn to think more outside the box, and actually come away from the book a more creative thinker and problem solver.

The first three questions are meant to be a warm-up. They should help to get you into the right state of mind and ready you for the unconventional surprises ahead.

Enjoy!

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Why are manhole covers round?

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Youre having a conversation with a friend about your favorite foods. He says to you, My favorite food is the one where you throw away the outside and cook the inside, then you eat the outside and throw away the inside! What food is he talking about?

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How far can a fox run into the woods?

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You are a stranger lost in a strange land. You are travelling along a road and come to an intersection where you can either go east or west. You know that one of these roads will lead you to your destination, and that the other will lead you to a hopeless despair. Standing at this fork in the road are two men who know the direction you must take to reach your destination. You know that one of these men always tells the truth and that the other always lies. Unfortunately, you cannot remember who is who. With only one question directed towards one of the men, how can you be sure to make the right choice and travel down the correct path?

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You have just purchased three things at the local market: a wolf, a duck, and a bag of seeds. To get back home you must travel across a river in a small boat. You are only allowed to have one item with you on your boat at any time. You cannot leave the wolf alone with the duck, because the wolf will eat the duck. You cannot leave the duck alone with the bag of seeds, because the duck will eat the seeds. How many trips on the boat must you take to be able to get the wolf, duck, and bag of seeds across to the other side of the river safely?

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What is the maximum number of sections into which a circle may be divided into by drawing four straight lines through it?

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You are making some French toast for breakfast. In order to cook a perfect piece of French toast you must fry each side of the slice of bread for thirty seconds. You only have one frying pan and it can only hold two slices of bread at a time. How quickly can you make three perfect slices of French toast?

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Your friend flips two coins behind your back and tells you: At least one of the coins came up tails. What is the probability that both coins came up tails?

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In front of you are three closed metal boxes. One is labeled Nuts, one is labeled Bolts, and one is labeled Nuts & Bolts. You know that every box is incorrectly labeled and you would like to rearrange the labels so that each box is correct. By making only one selection from one box, how can you be sure to properly re-label each box?

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You have a delicious round birthday cake. How many equal-sized pieces can you cut the cake into by making only three straight slices with a knife and without moving any of the pieces?

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You are in an empty room with a glass of water. The glass is a right cylinder that looks like it is about half-full, but you are not quite sure. What is the most accurate way, without spilling any water, to determine whether the glass is half-full, more than half-full, or less than half-full?

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A thin four-foot long chain is suspended by its ends and nailed to a wall. Both nails are level with one another and parallel to the floor. Because of gravity, the middle part of the chain hangs down towards the floor. If the vertical length of the chain is two feet, what is the distance between the two nails?

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You and your best friend have loved the same girl since kindergarten. After years and years of discussions, arguments, and fights, you have both decided to settle the matter with a coin toss. The only coin available to you is an old wooden nickel and you are certain that it comes up heads more than 50% of the time. How can you be sure to have a fair contest that is based purely on chance by only flipping this coin?

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You and two of you friends would like to know the average of all of your salaries. You are each self-conscious about the amount of money you make and will not tell one another your salaries. What can you do to figure out the average salary?

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You have a 5-gallon bucket, a 3-gallon bucket, and a water faucet. How can you accurately put four gallons of water into the 5-gallon bucket?

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A man is imprisoned in a ten-foot by ten-foot by ten-foot room. The walls are made of concrete, the floor is made out of dirt, and the only openings are a locked door and a skylight. The man has a small shovel and starts to dig a hole in the floor. He knows that it is impossible to tunnel out of the prison cell, but he continues to dig anyways. What is the mans plan?

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An old wise man lived in a little home on a hill. One morning, two young boys from the town decided they wanted to fool the wise man. They took a dove with them and knocked on the old mans door. When he answered, one of the boys said to him: Lets see how smart you really are! Is the dove Im holding behind my back dead or alive? The old man smiled and replied, I cannot answer you because I know you are trying to trick me. Despite knowing the condition of the dove, why wouldnt the wise old man answer the young boy?

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You are a prisoner in a strange land. You have been sentenced to death but are being given one chance to live. The king of the land has decided to let you play a simple game to determine your fate: You are presented with two clay jars, one containing 100 white stones, and one containing 100 black stones. You are allowed to redistribute these stones any way that you like, but when you are finished all stones must be in the jars. After you have finished, both jars will be shaken up, you will be blindfolded, and you will be presented one of the two jars at random. You will pick one stone out of the jar given to you. If the stone is white, your life will be spared, if the stone is black, you will be executed immediately. How should you redistribute the stones to give yourself the best chance of survival?