4. 10 (This one is a bit of a Joke :D)

A man leaves his house every morning to walk to work and passes a mental hospital surrounded by a wooden fence. Every morning the patients are out in the yard and he can hear them saying in unison,

“10, 10, 10, 10, 10”.

One day, he gets curious and looks through a hole in the fence.

Suddenly, a stick shoots out and pokes him in the eye.

“FUCK! He says to himself.”

While walking away pissed off he can hear the patients saying,

“11, 11, 11, 11, 11”