A soccer team just became first in the national league. The players which were on the field just after the referee blew the final signal wanted to congratulate each other by shaking hands. Assuming that each player shook hands with every other player only once, how many time were the hands shaken in total? (There are of course 11 players in a soccer team)

A bookworm eats a straight way through a encyclopedia consisting of ten parts. Each part has 1000 pages. The bookworm starts on the front cover of the first part and ends on the back cover of the last part. From how many pages did the bookworm eat?

Close one of your two eyes. Move your head close to the monitor and watch concentratedly to the left circle if you closed your left eye. You should look to the right circle if you closed your right eye. Keep watching and move your head slowly backwards while checking the other circle. What happens? And how is that possible?