Math Riddles


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: 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: There is a chain nailed to the wall. The chain is 10 feet long and the center of the chain dips down 5 feet from where each side of the chain is nailed to the wall. How far are the 2 ends of chain from each other?

Question: What is the next number in the sequence? 1 11 21 1211 111221 312211