Engineer, physicist and mathematican are all challenged with a problem: to fry
an egg when there is a fire in the house. The engineer just grabs a huge
bucket of water and runs over to the fire, putting it out. The physicist
thinks for a long while, and then measures a precise amount of water into a
container. He takes it over to the fire, pours it on and with the last drop
the fire goes out. The mathematican pores over pencil and paper. After a few
minutes he goes "Aha! A solution exists!" and goes back to frying the egg.
Sequel: This time they are asked simply to fry an egg (no fire). The engineer
just does it, kludging along; the physicist calculates carefully and produces
a carefully cooked egg; and the mathematican lights a fire in the corner, and
says "I have reduced it to the previous problem."