A girl was fond of collecting rare stamps. When she was twenty years old, she bought a box to collect her stamps. On her every birthday, she put 250 stamps in it and her sister who was also fond of collecting stamps took out 50 stamps from it on her birthday. The girl met an accident when she was 60 years old. When her box was opened, there were only 500 stamps in it.

How is it possible logically?

The girl was born on 29 February, thus she put 250 stamps every four years.

In forty years, she put stamps only 10 times which makes the total of 2500 stamps.

Her sister was born on any other day and she took out 50 stamps from the box forty times which makes the total stamp she took out to be 2000.

Thus after forty years, the girlâ€™s box had only 500 stamps.