Assuming ........

As an experiment, an engineer, a physicist, and a mathematician are placed in separate rooms and left with a can of food, but no can opener. A day later, the rooms are opened, one-by-one.
In the first room, the engineer is snoring, with a battered, opened and emptied can. When asked, he explains that when he got hungry, he beat the can to its failure point.
In the second room, the physicist is seen mouthing equations, with a can popped open beside him. When asked, he explains that when he got hungry, he examined the stress points of the can, applied pressure, and "pop!"
In the third room, the mathematician is found sweating, and mumbling to himself, "Assume the can is open, assume the can is open..."

ok, no comment ......