An engineer, a physicist and a mathematician are staying in a hotel while
attending a technical seminar.

The engineer wakes up and smells smoke. He goes out into the hallway and sees a
fire, so he fills a trash can from his room with water and douses the fire. He
goes back to bed.

Later, the physicist wakes up and smells smoke. He opens his door and sees a
fire in the hallway. He walks down the hall to a fire hose and after calculating
the flame velocity, distance, water pressure, trajectory, etc. extinguishes the
fire with the minimum amount of water and energy needed.

Later, the mathematician wakes up and smells smoke. He goes to the hall, sees
the fire and then the fire hose. He exclaims, Ah, a solution exists! and then
goes back to bed.