A man's car runs out of gasoline. His car tank holds exactly 13 gallons. He has three empty unmarked containers which can hold 3 gallons, 6 gallons, and 11 gallons. Using only these containers at the gas station, how can the man bring back exactly 13 gallons?

(He is not allowed to buy over 13 gallons and dispose of the extra.)

Ok, first, the man should fill up the 11-gallon. Then he will use the gasoline in the 11 to fill the 3 and 6. Then he will have 2 gallons of gas in the 11. next, he should empty out the 6 and 3 back into the gas tank. Then he purs the 2 gallons in the 11 into the three, and fills up the 11 again. Then he has 2 gallons in the 3-gallon, and 11 gallons in the 11-gallon, making 13 gallons.

Sorry, I know this is a bit confusing, but read carefully and draw some pictures or something and it should make sense. 

Posted by saprom on 2005-12-21 20:39:29