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## Math for fun and glory

### Course: Math for fun and glory>Unit 2

Lesson 1: Brain teasers

# Alien abduction brain teaser

Saving Earth from becoming a mushroom farm. Created by Sal Khan.

## Want to join the conversation?

• A beggar's brother died, but the man who died had no brother.
How could this be?
• The beggar is a girl because it doesn't say that the beggar was a boy we just assumed that.
• Is there a way to save everyone?
• There is a 50 50 chance that the first person will live, so technically if he gets it right all the people could be saved.
• I have a teaser:

A soldier needs to store his 70-centimeter sword, but the only chest available measures 40 centimeters long, 30 centimeters wide, and 50 centimeters high. Will the sword fit in the chest?
• Sometimes, I try to fit myself in a small box, and I fit myself in the diagonal. So I will attempt to prove that the soldier may do this with his sword.

The diagonal of a rectangular prism is the hypotenuse of a triangle whose legs are the diagonal of the bottom and the height of the rectangular prism. So the diagonal of the chest is √((50 cm)² + ((30 cm)² + (40 cm)²)). This is 70.7106... cm. The diagonal of the chest is just 0.7106... cm longer than is necessary to store the sword, so yes, the sword will fit in the chest.
• I know that the other way works too, but that system means that you have to remember everything that everyone else said. If one person messes up, the rest of the people are thrown off. I propose that, if the person next in line is wearing a green hat, the person behind them immediately answers with their hat color. If the person in front of them is wearing a purple hat, the person pauses for a moment, then they answer the question.
• No information can be communicated by verbal trickery. This includes uses silence as an indicator of information. "Information" here has a precise definition that forces you along a logical pathway. Nice try, but it is technically cheating.
• Awesome! Puzzle....those aliens would be cynical to judge humanity based on our ability to reason.. what if humans were still primitive and had not discovered math or logical reasoning.. they would kill us!
• They would know if we were primitive, and if they are democrats the votes to kill them would be 23 against 65 or something like that. One does not simply judge a fish by its ability to climb a tree, because they don't climb trees.
• one guy have 50% to live..... which is very unfair....... there there is not justice nor fairness in the word....... and I cant believe i live in this kind of place..... so the question is, will there be a way to save the last guy?? I mean like for sure. 100%
• @sbowden514 What do you mean? African or European swallow?
• What if the guy in the back is very short?
or the aliens told you not to look leaning to the side?

WELL, HAVING A MIRROR WILL BE THE MOST USEFUL THING
• Cant the last guy just say the color of the guy in front of him and onword..
• no because if they say the color of the person in front of him the person in front of him would have to say his color, not the next person's color in order to be saved.