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.)
First, the man uses the meter on the gas pump to measure out precisely 13 gallons.
Then, he puts 11 in the large container and the remaining 2 gallons in one of the others.