This is my dad's (a math major) favourite joke. What's the difference between an Engineer and a Mathematician? A mathematician and an engineer are living together in a dorm when a fire starts in their room. The mathematician wakes up and sees the fire. He quickly scans the room and sees a fire extinguisher and goes back to bed, happy knowing a solution exists. The engineer wakes up, sees the fire and uses the extinguisher to put it out.