Crossing a Bridge riddle
Four men want to cross a bridge. They all begin on the same side. It is night and they have only one flashlight with them. At most two men can cross the bridge at a time and any party who crosses, either one or two people, must have the flashlight with them. The flashlight must be walked back and forth: it cannot be thrown, etc. Each man walks at a different speed. A pair must walk together at the speed of the slower man. Man 1 needs 1 minute to cross the bridge, man 2 needs 2 minutes, man 3 needs 5 minutes, and man 4 needs 10 minutes. For example, if man 1 and man 3 walk across together, they need 5 minutes.
How can all four men cross the bridge in 17 minutes?
First man 1 and 2 cross the bridge, it will take them 2 minutes.
Then man 1 goes back in 1 minute.
Next man 3 and 4 cross the bridge in 10 minutes.
Man 2 returns taking 2 minutes.
And last, man 1 and 2 cross in 2 minutes.
total 2+1+10+2+2=17 minutes.
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