# Letter folding - math puzzle

If you would fold a letter in two fifty times, how thick should the enveloppe be that can fit the letter? Assume that the thickness of a piece of paper is about 0.05 mm.

# 2 x 2 = 2 + 2 - math puzzle

Two times two is equal to two and two. But are there more number pairs for which the sum of the numbers is is equal to the product of the numbers? The numbers may be different. |

# Chess-board - math puzzle

How many different squares are located on a chess-board? |