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  Number & Math Play

Toast For Three
 
Q Dad is preparing breakfast for his three children ? Dan, Ed, and Frank. Each boy wants Dad to toast 1 slice of bread for him. The family's toaster holds only 2 slices of bread and toasts only 1 side at a time. The person who toasts bread has to toast one side of a slice of bread, take out the slice, turn it over, and put it back in the toaster to toast the other side. It takes exactly 1 minute to toast 1 side of a piece of bread. Dad has figured out how to toast 3 slices on both sides in only 3 minutes. How does he do it?


 
A First minute: Dad toasts Dan's bread on side 1 and Ed's bread on side 1. Then he removes Dan's slice, turns it around, and puts it back in the toaster. He puts Ed's slice aside and puts Frank's bread in the toaster. Second minute: Dad toasts Dan's bread on side 2 and Frank's bread on side 1. He removes both slices, turns Frank's around, and puts it back in the toaster. He gives Dan his toast and puts Ed's slice back in the toaster. Third minute: Dad toasts Frank's slice on side 2 and Ed's slice on side 2. Then he serves those slices to Frank and Ed.

Inspired by a puzzle in Mathematical Puzzles by Martin Gardner. New York: Thomas Y. Crowell Company, 1961.