In the puzzle Four people on a Bridge we met four people who needed to cross a bridge at night. In this puzzle, there are five people who must cross two sequential bridges at night. As in the original puzzle, there are some hindrances:

The bridges can only support two people crossing at a time.

Each person has a different speed in which they can cross: 10 minutes, 7 minutes, 5 minutes, 2 minutes, and 1 minute.

They have only two flashlights to share among them.

What is the shortest amount of time it will take for all five people to cross both bridges?

I have them all crossing in twenty six minutes.  Which I believe is the fastest valid solution submitted yet.  

a=10, b=7, c=5, d=2, e=1

a&b=10 min bridge 1, a&b 10 min bridge 2==>20 minutes

c&e begin bridge one after 10 minutes (a&b off, crossing bridge 2)

5 minutes across, e 1 min back, d&e 2 min across==>8 min

use same pattern for bridge 2==>8 min

10+8+8=26 min

I think this is the fastest submitted, but there still maybe faster.

 

Edited on June 27, 2005, 7:20 pm

Edited on June 27, 2005, 7:27 pm

Posted by john on 2005-06-27 19:12:32