May 02, 2020
RAY: Roger Meyer sent this puzzler in.
A group of explorers was trapped in Alaska for the winter season. Stuck in the ice and snow, they only had one means of escaping to civilization before spring: an old World War Two airplane with skis, which they could use in the event of an emergency.
The plane had a placard on the instrument panel that said, "Do not attempt to start the engine with oil temperature below minus forty degrees Fahrenheit."
Well, wouldn't you know, a medical emergency arose, and when the pilot checked the oil temperature gauge, he discovered it was broken. As luck would have it, this being an international kind of team, all of their instruments were in Centigrade. Unfortunately, nobody could remember the formula for converting Centigrade to Fahrenheit.
Skip, who had been carefully looking over the engine for the last couple of days, emerged from the inky shadows of the dimly lit Quonset hut. The others asked, "Do you know the formula for converting Centigrade to Fahrenheit?" He said, "I don't need no stinkin' formulas. But I know you can start the engine. It will be all right."
Sure enough, they started the engine up, and it was fine.
The question is, how did Skip know they could safely start the engine?
RAY: The formula happens to be Fahrenheit equals 9/5th Centigrade plus 32. If you put 40 degrees in, or minus 40 degrees in for F, C comes out minus 40 also. What Skip knew, even though he didn't know the formula, is that if it was above minus 40 Centigrade, it had to be above minus 40 Fahrenheit.