Math Riddles

Question: A rat is placed at the beginning of a maze and must make it to the end. There are four paths at the start that he has an equal chance of taking: path A takes 5 minutes and leads to the end, path B takes 8 minutes and leads to the start, path C takes 3 minutes and leads to the end, and path D takes 2 minutes and leads to the start.

What is the expected amount of time it will take for the rat to finish the maze?

Question: There are 100 coins scattered in a dark room. 90 have heads facing up and 10 are facing tails up. You cannot tell which coins are which. How do you sort the coins into two piles that contain the same number of tails up coins?

Question: John has been hired to paint the numbers 1 through 100 on 100 apartments.

How many times with he have to paint 8?

Question: There are several books on a bookshelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

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