Riddles, Brain Teasers, & Jokes

[quote]horsepuss wrote:
How bout a paradox, this is one of my favs

The grandfather paradox.

suppose a man travelled back in time and killed his biological grandfather before the latter met the traveler’s grandmother. As a result, one of the traveler’s parents (and by extension the traveller himself) would never have been conceived. This would imply that he could not have travelled back in time after all, which in turn implies the grandfather would still be alive, and the traveller would have been conceived allowing him to travel back in time and kill his grandfather.

[/quote]

To solve this, the guy would always fail to kill his grandfather.

Riddle
A triangle has three sides that measure 13, 18 and 31 inches. What is the triangles area?

Brain Teaser
A man and a women are driving along a country road on a cold winter night when the car breaks down. Before leaving to find help, the man tells the women to open the doors or windows to let anyone in. He leaves and she does what he says. When he returns, she is dead and there is a stranger in the car. What happened?

Joke
Knock Knock
Whoâ??s there?
Queen!
Queen who?
Queen as a whistle!