Vol. 46, No. 1
The two guards:
One approach is to ask one guard: "Were I to ask you if the door on the right was the correct one, what would you say?" The truthful guard would answer yes (if it’s the correct one), or no (if it’s not). If you ask the guard who always lies whether the same door is the correct one, he would answer no. But if you ask him: "If I was to ask you if this door were the correct one, what would you say?" he would be forced to lie and say yes. When you get two identical answers about the same door, you’ve solved it.
White house paint:
Employers use questions like this to see how the candidate approaches the problem and all its subtle variations. For example, taking interior walls into account would certainly indicate broader thinking. Here’s how one candidate answered: Start with the basic assumption that there are 270 million people in the United States. Perhaps half of them live in houses. The average family size is about three people, so that’s 45 million houses. Add another 10 percent for second homes, and you get 50 million houses. If houses are painted every 10 years, on average, then there are 5 million houses painted every year. Assuming that one gallon of paint covers 100 square feet of wall, and that the average house has 2,000 square feet of wall to cover, then each house needs 20 gallons of paint. So 100 million gallons of paint are sold per year.
The prisoner’s cigarette:
This question, posed by a large mergers and acquisitions firm, essentially tests for creative negotiating skills. The answer they want is something like: "Threaten to kill yourself by smashing your head against the wall of your cell. That gives you leverage with the guard. He’d be tied up doing paperwork and would miss weekend time with his family (remember, it’s Friday afternoon), so he’ll give you a cigarette."