There are 4 men who want to cross a bridge. They all begin on the same side.
You have 17 minutes to get all of them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 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 a rate of the slower man's pace.
Man 1: 1 minute to cross.
Man 2: 2 minutes to cross.
Man 3: 5 minutes to cross.
Man 4: 10 minutes to cross.
For example, if Man 1 and Man 4 walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Man 4 returns with the flashlight, a total of 20 minutes have passed, and you have failed the mission. See how quickly you can solve this!
P.S.
The flashlight cannot shine a long distance. No one can be carried, etc. (This is a straightforward problem. There are no tricks.)