A man has a barrel filled with oil that weighs 100 pounds, and then he puts something into it. Now the barrel weighs less than 100 pounds. What did he put in the barrel?

What have one eye but still cannot see?

If eleven plus two equals one, what does nine plus five equal?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

What is at the end of a rainbow?

A train leaves from point A for point B at 80 mph. After half an hour, another train leaves from point B for point A at 60 mph.

Which of the trains will be farther from point A when they meet ?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

What is next number in the pattern below:

131 517 192 123 ?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

Andrew sees a very rare bird named "Ruppell's vulture". Soon Andrew was dead. Can you explain the mystery, Mr. Sherlock?