#36

There are 4 people at a bridge: A, B, C, and D. It takes A 1 minute, B 2 minutes, C 5 minutes, and D 10 minutes to cross the bridge. They can cross alone or in pairs, but each single or pair must carry a flashlight with them. There is only one flashlight and it cannot be thrown. What is the shortest time that it will take A, B, C, and D to traverse the bridge?

Answer:

17 minutes.

A + B goes = 2min
A returns = 1min
C + D goes = 10min
B returns = 2min
A + B goes = 2min