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 think I understood the problem based off the 4 version one... my solution doesn't allow for illuminating the bridge though as some have suggested.
10&7 starts off together at the speed of the slowest of them which is 10 minute for 1 bridge. By the time they get off first bridge and start on the second bridge (10 minute), 5&1 starts off the first bridge and make it in 5 minutes, 1 goes back for (6 minutes total), while 5 waits between the two bridges, and brings 2 back with him for a total of 8 minutes)... at that point 10&7 are still not off the second bridge so they have to wait another 2 mins.
The point is since they have to wait for 10&7 to be off second bridge, the 8 minutes they took to get off first bridge (1&2&5) is meaningless... so it takes them another 8 minutes to all get off second bridge post-time when 10&7 got off second bridge.
Total, 10+10+8=28
my solution
