Bridget Ilene Delaney (kagomeshuko) wrote in mental_workout,
Bridget Ilene Delaney
kagomeshuko
mental_workout

U2 Bridge Crossing

My mom got this puzzle:

U2 has a concert that starts in just 17 minutes and all of the
band members must all cross a bridge to get there. The four men
begin on the same side of the bridge and you must help them to
get across to the other side.

Due the age of the bridge, a maximum of two people can cross at
one time. To make matters worse, it is night-time and there is
only one torch. The torch is always required when crossing the
bridge and the torch must be walked back and forth, it cannot be
thrown, etc. Each band member walks at a different speed and a
pair must walk together at the rate of the slower man:

Bono takes 1 minute to cross
Edge takes 2 minutes to cross
Adam takes 5 minutes to cross
Larry takes 10 minutes to cross

For example, if Bono and Larry walk across first, it takes them
10 minutes to cross. If Bono then returns with the torch, a
total of 11 minutes will have passed. There is no trick behind
this, it is the simple movement of resources in the appropriate
order.


I'm guessing the question is how do you get them all across and what is the shortest amount of time that can be gotten to get them all across?
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