The Bridge and Flashlight Puzzle

Four people need to cross a rickety bridge at night, but they must use a single flashlight to see where they’re going. The bridge can only hold two people at a time, and both must move at the speed of the slower person. The flashlight must always be carried across the bridge, meaning someone must bring it back for the next group.

Each person takes a different time to cross:

Person A: 1 minute
Person B: 2 minutes
Person C: 5 minutes
Person D: 10 minutes

How can all four people cross the bridge in just 17 minutes?

Steps to Cross in 17 Minutes:

A & B cross first (2 minutes) → A carries the flashlight.
- Now A & B are on the far side.
A returns with the flashlight (1 minute) → Now only A is on the starting side.
C & D cross together (10 minutes) → B holds the flashlight.
- Now C & D are on the far side with B.
B returns with the flashlight (2 minutes) → Now only B is on the starting side.
A & B cross again (2 minutes) → Now everyone is on the far side.

Total Time:

2 + 1 + 10 + 2 + 2 = 17 minutes