Tuesday, December 20, 2005

Crossing a Dark Bridge Quickly

Four people are trying to cross a narrow broken bridge in the middle of the night. It is very dark, so they need a flashlight in order to see where all the broken planks are when crossing the bridge. Luckily, they have a flashlight, but only one. Unfortunately, the bridge can only support two people at a time, so they can at best cross in pairs.

The four people can walk across at different speeds: 1, 2, 5 and 10 minutes to cross the bridge. When two people cross, they cross the speed of the slower person.

What is the fastest time possible to get all 4 people safely across the bridge?

Hint: It is less than 19 minutes.

1 comment:

Mike said...

17 minutes?