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Question 482392: There are 4 members of a band, and they all walk at different rates. Only 2 people can cross the bridge at the same time, and the two peopl have to wal at the same sppeed of the slowest walker. Whoever goes across the bridge has to have a flashlight and so someone must always carry the flashlight. Here is how long it takes each person to cross the bridge. Tyler 1 minute, Beach 2 minutes, Grace 5 minutes and coleen 10 minutes. you cannot cary another person or toss the flashlight back across the river. Can you find a way to get everyone across in no more than 17 minutes if so explain if not explain
Found 2 solutions by scott8148, Edwin McCravy:
Answer by scott8148(6628)   (Show Source):
Answer by Edwin McCravy(20055)  (Show Source):
You can put this solution on YOUR website! There are 4 members of a band, and they all walk at different rates. Only 2 people can cross the bridge at the same time, and the two peopl have to wal at the same sppeed of the slowest walker. Whoever goes across the bridge has to have a flashlight and so someone must always carry the flashlight. Here is how long it takes each person to cross the bridge. Tyler 1 minute, Beach 2 minutes, Grace 5 minutes and coleen 10 minutes. you cannot cary another person or toss the flashlight back across the river. Can you find a way to get everyone across in no more than 17 minutes if so explain if not explain.
Let's nickname Tyler "#1"
Let's nickname Beach "#2"
Let's nickname Grace "#5"
Let's nickname Colleen" "#10".
Let's nickname the river "R"
We start with the 4 people and the river in this order
Order #1,#2,#3,#4,R
#1 and #2 go across which takes 2 minutes
Order is now #5,#10,R,#1,#2
#2 returns with the flashlight which takes 2 minutes
Order is now #2,#5,#10,R,#1
#5 and #10 go across, which takes 10 minutes
Order is now #2,R,#1,#5,#10
#1 returns with the flashlight which takes 1 minute
Order is now #1,#2,R,#5,#10
#1 and #2 go across, which takes 2 minutes
Order is now R,#1,#2,#5,#10
--------------------------------------------------------
Total time 17 minutes
Edwin
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