A group of four people has to cross a bridge. It is dark, and they have to light the path with a flashlight. No more than two people can cross the bridge simultaneously, and the group has only one flashlight. It takes different time for the people in the group to cross the bridge:Scary's used to running for the loo, so he crosses the bridge in 1 minute,
Dawn crosses the bridge in 2 minutes (because it's a female bridge, and if it was male she would take twice as long),
Aled crosses the bridge in 5 minutes (following a promise of beer the other side),
Rik is big and slow, so crosses the bridge in 10 minutes.
How can the group cross the bridge in 17 minutes?
