One day a mathematician decides that he is sick of math. So, he walks down to the fire department and announces that he wants to become a fireman.
The fire chief says, “Well, you look like a good guy. I’d be glad to hire you, but first I have to give you a little test.”
The fire chief takes the mathematician to the alley behind the fire department which contains a dumpster, a spigot, and a hose. The chief then says, “OK, you’re walking in the alley and you see the dumpster here is on fire. What do you do?”