Riddles

I love them. Here are a few good ones. If you have any questions, comments, solutions, or furstrations, you can message me on Twitter @jeffclune.

An important part of the riddling process is trusting the riddler. During those frustrating moments in which you do not know the answer you will frequently wonder if the solution is going to be weak. You'll just have to trust me... On this page I will only ask great riddles. What makes a great riddle? That an answer exists such that once it pops into your head you know it is right without having to ask.

I riddle you these...

The Scarlet Edict

A chief calls the women of her village together and announces that murder has been committed in their midst. She tells the women that they are to report to the fire circle in the morning. At that time, if any woman knows that her husband is guilty of the crime, she is ordered to step forward and denounce him. They are also told that doing so will lead to his immediate execution. Finally, given that the chief does not want to start feuds among the women in the tribe, who typically retaliate against the messenger, no one is allowed to communicate about who might be guilty.

The women break to ponder the news. They reflect on the odd properties of the village, of which there are two:

a) True to the idiom 'the partner is last to know,' each woman knows everything about the activities of every man in the town except her own partner.

b) It is inconceivable for a tribe member to fail to follow the orders of the chief. The chief is also bound by her own law.

The next morning the women of the tribe are assembled. The chief gives the signal but no one denounces her husband. Blood is thus not shed. The chief announces that they will have to come back the following morning—and each morning until the problem is sorted out.

On the second morning no blood is shed.

On the third morning blood is shed.

How many people were killed?

A Wizard's Justice

A wizard comes home to find his three apprentices misbehaving. Enraged, he decides to punish them severely. Knowing that he is a sporting wizard, the three ask him to at least make a game of it. He can't refuse and sets up the following:

Each apprentice, we will call them A, B, and C, is placed facing forward on a straight (not winding) staircase. A is at the top, B in the middle, and C at the bottom. So, A can see B and C. B can see C, and C is looking at the wall. The wizard places a blindfold on all three of them and then places a blue or red pointy wizard cap on each of their heads. He then freezes their bodies so they cannot move.

The wizard then tells the lads that he has placed at least one red and one blue cap in the group (they do not know whether there are 2 reds and one blue or 2 blues and one red). He also relays that he is going to remove the blindfolds and that it is up to one of them to correctly shout out the color of the cap on their head within five seconds. If any of them say anything other than the color of the cap being worn by the speaker, they are all newted. If one of them can correctly name the color of their cap, they all go free.

All set? The wizard removes the blindfolds and four seconds later apprentice B shouts out the correct answer. He is right. How did he know what color the cap on his head was?

Prisoner's Conundrum

Sixteen prisoners are told they will get a chance to be released if they can win the game the wardens are setting up. The prisoners will be able to meet ahead of time and agree upon a strategy. The rules:

Each prisoner will be taken from her cell into the game room at the prison. In the game room will be two switches that can either be in the on (up) or off (down) position. The switches are not attached to anything (like lights). The prisoner must flip one and only one of the switches (from on to off or vice versa) and then is escorted back to her room. Prisoners will be selected at random and any one of them may be led into the room many times before another has visited once. At any point, a prisoner can declare "We've all been in here." If she is right, and all the prisoners have indeed been in the room, then they all get to go free. If at least one prisoner has never been taken into the room, they lose and are all forced to do three years of hard labor.

Motivated by the horror of that possibility (caring little for their freedom), they strike upon a strategy that will never err. What is it?

Will Work for Utopia

The Egyptians weighed your heart to see if you made it to the Promised Land. In the States, it's all about the gold.

Since you're broke, you ask the gatekeeper if you can work your way in. The bored manager at the local St. Peter's Gates, Inc. franchise offers to make a game of it. He will only let you in if you can help him weigh some of the gold he has collected.

He places 10 bags of coins in front of you that contain 50 coins each. He knows that one of the bags is full of counterfeit coins and wishes to send the counterfeiter to hell for trying to skimp. Legitimate coins weigh 1 ounce whereas counterfeit coins are 1/100th of an ounce lighter than normal coins. He challenges you to figure out which bag is full of the faux coins.

To make it interesting, he tells you that you only get one weighing on his scale (e.g., one readout). The scale is a digital one.

How do you determine which bag has the coins that weigh less?

Taking Your Business Elsewhere

You find yourself in front of two doors: one goes to heaven, and one goes to hell (you clearly didn't do very well on that whole scale thing and decided to try the St. Peter's down the street). There is a man standing in front of each door. One always tells the truth, and one always lies. You don't know which man is standing in front of which door. You can only ask one question of one man. What do you ask to find out which door goes to heaven?

Unnamed

What is no sooner spoken than broken?

Nine Ball

You have a balance scale (picture the statue of blind justice). There are nine marbles. Eight of them weigh the same amount. One of them is heavier than the others. How can you tell me which marble is the heavy one with only two uses of the scale?

— Very easy

What Am I?

Always runs, but never walks,
Has a mouth, but never talks.
Has a bed, but never sleeps,
Has a head, but never weeps.

What am I?

Unique Creatures

We are very different creatures,
We all have unique features.
The first of us in glass is set.
The second you will find in jet.
The third is found in tin,
And the fourth is boxed within.
If the fifth you shall pursue,
It will never fly from you.

What are we?

Imbalance

You have twelve marbles. Eleven weigh the same and one is either heavier or lighter than the others. You do not know whether the ball is heavier or lighter. You can use the scales three times and must tell me which marble is the anomaly and whether it is heavier or lighter than the rest.

— This one was given to me by my PhD advisor in around 2007. I never got around to focusing on it until 2024 on vacation, when I finally solved it after nearly 20 years. Never give up!

All Sorts

We are very different creatures. We all have unique features. The first of us in glass is set. The second you will find in jet. The third of us is found in tin, and the fourth is boxed within. If the fifth you shall pursue, it will never fly from you. What are we?

Hyperbole

What's greater than God and more evil than the Devil. The rich want it and the poor have it. If you eat me I die.

Sorting

If you have two buckets and 100 white and 100 black marbles, how do you distribute them between the two buckets such that you maximize the chance of finding a white for a person who randomly chooses a bucket and then within it randomly chooses a marble? (Note, you have to put all 200 marbles in one of the two buckets). You can get the probability of getting a white above 50%.

Clean Room

A professor offers a deal to his class with 100 students. They all give their student IDs to him, and he puts them in boxes. He lines up the boxes on a shelf in a random order. He then allows the students to come into the room one at a time and open 50 boxes. If they find their own ID, they pass; if not, they fail. The boxes are set up identically for all students, and they cannot talk once the process starts, so no direct information can be passed.

He offers them a deal. They must all pay him $1 to play. If ALL 100 of them pass, then they each get $100. If ANY fail, they don't get any money.

Is it worth playing?

— The students can plan out their strategy ahead of time, which is, of course, the real trick. What this really comes down to is what is the probability of them all getting it right. You know that the first person has a 50% chance of getting it right, so that's the best you can hope for. Of course, if everyone picks randomly, that's 1 in 2100, which is terrible odds! So can they come up with a better plan?

— This one is very hard. There is a great Veritasium video explaining the answer to this one (once you are ready to look!)

Let me know if you know of other good ones I should post!