A mathematician is going for a job as a firefighter. The chief asks him "if you see a bin on fire in an alleyway, what do you do?""Well, I would make sure it's safe to enter the area, check for electrical hazards, then hose it off or call for help."
"Good. So what if you see a bin in an alleyway that looks like it might catch fire?"
"I'd set it on fire, reducing the problem to one I have already solved ..."