then tough one

[metzo]

Originally posted by sarettah@Nov 18 2004, 12:48 PM
Heres one for you that my daughter and I played with the other night:

Scenario: Pitch black night. 4 men are traveling with one lantern amongst them. They come to a bridge across a very deep ravine. The bridge is only wide enough and strong enough to support 2 of the men at a time. There is no railing or side on the bridge so because of the darkness you cannot go over the bridge without the lantern and furthermore no man dares to go across the bridge without being in actual contact with the lantern.

Man 1 can cross the bridge in 5 minutes
Man 2 can cross the bridge in 10 minutes
Man 3 can cross the bridge in 20 minutes
Man 4 can cross the bridge in 25 minutes

What is the least amount of time that it can take for all 4 men to cross the bridge ?

The least amount of time for all 4 men to get across the bridge would be 1 hour and 5 minutes...

Man 1 goes across with Man 2 - 10 mins
Man 1 goes back with the lantern - 5 mins
Man 1 and Man 3 go across - 20 mins
Man 1 goes back - 5 mins
Man 1 and Man 4 go across - 25 mins