Brainteasers

A brainteaser is a problem for which it is hard to find the answer, especially one which people enjoy trying to solve as a game. Try solving the brainteasers below and ... have fun !

1-If a water lily (nenúfar) doubles its size everyday, and if it takes ten days to cover a lake, how long does it take to cover half the lake  ?

2- A farmer has to cross a river in a small boat .He can only take one animal with him in his boat. He has a bird, a cat and a dog. But he cannot leave the bird  and the cat alone, for the cat will kill the bird.And he cannot leave the cat and the dog alone, for the dog will kill the cat. How can he take all the animals safely across the river ?

3-Brothers and sisters I have none but that man's father is my father's son. Who  is the man the speaker is talking about ?

4-There are 22 rows of bricks (hileras de ladrillos)  in a wall. Every hour a snail (caracol) climbs two rows of bricks and then slides back  (  se desliza hacia atrás) one row. How many hours does the snail take to climb to the top of the wall ?

Answers to brainteasers

1- Nine days.On the ninth day the lily covers half the lake, it doubles and covers the whole lake on  the next day.

2- The farmer crosses with the cat and comes back alone. The farmer crosses with the bird but comes back with the cat and then crosses the river with the dog. He comes back and then crosses the river with the cat.

3-The speaker is talking about his son.

4-21 hours. During the last hour the snail climbs two rows of bricks to the top of the wall and so it does not slide back.