Math Riddles

Question: You have two coconuts and you want to find out how high they can be dropped from a 100 story building before they break. But you only have $1.40 and the elevator costs a dime each time you ride it up (it's free for rides down).

How can you drop the coconuts to guarantee you will find the lowest floor they will break at, while starting and ending at floor 1?

Note: They break when dropped from the same height and they don't weaken from getting dropped.

Question: If 1/2 of 5 is 3, then what is 1/3 of 10?

Question: Four people need to cross a bridge in 17 minutes in the middle of the night. The bridge can only hold two or less people at any time and they only have one flashlight so they must travel together (or alone). The flashlight can only travel with a person so every time it crosses the bridge it must be carried back. Tom can cross in 1 minute, John can cross in 2 minutes, Sally can cross in 5 minutes, and Connor can cross in 10 minutes. If two people cross together they go as fast as the slower person.How can they cross the bridge in 17 minutes or less?

Question: In an apartment complex in New York there are one hundred married couples. When one of the husbands cheats on his wife with one of the other wives, his wife has no idea. With the large amount of gossip in the complex, all of the other wives know he is cheating. If a wife finds out that her husband is cheating on her, she kills him the following morning. Someone anonymously sends an email to all of the wives in the building saying that at least 1 man is cheating on his wife in the building.

How many husbands will be killed and how long will it take?

Question: You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?

The glass is a right cylinder.