Girl and Boy - Solution

The Puzzle: A boy and a girl are talking.

"I am a boy" - said the child with black hair.

"I am a girl" - said the child with white hair.

At least one of them lied. Who is the boy and who is the girl?

The Solution . . .

They both lied. The child with the black hair is the girl, and the child with the white hair is the boy. (If only one lied they would both be boys or both be girls)

Gears 2 - Solution

The Puzzle: There are five gears connected in a row, the first one is connected to the second one, the second one is
connected to the third one, and so on.

How much faster would the last gear be if the second gear was twice the size of the first gear, and all the other gears were the same size as the first gear?

The Solution . . .

The last gear would be the same speed.