SOLUTION: Four men want to cross a bridge at night. They only have 17 minutes of flashlight battery, and it needs to be carried back and forth across the bridge (can't be thrown). The bridge
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Question 774712: Four men want to cross a bridge at night. They only have 17 minutes of flashlight battery, and it needs to be carried back and forth across the bridge (can't be thrown). The bridge is a width such that a maximum of 2 people can cross at a time. One man takes 10 minutes, another takes 5 minutes, another takes 2 minutes, and the last takes 1 minutes to cross. In what order will they have to cross to get everyone across the bridge before 17 minutes is up?? Answer by KMST(5328) (Show Source):
You can put this solution on YOUR website! Send the two fastest guys first.
That first trip across would take minutes.
Next, send one of them back with the flashlight. It does not matter which one.
The fast guy that goes back hands the flashlight over to the slow guys.
Next, the two slow guys cross together, using another minutes of battery use.
After they cross, the slow guys hand the flashlight to the other fast guy at the other side.
That fast gut goes back to pick up his fast friend, and they cross together in minutes.
The three trips in the right direction take minutes:
The two trips back to bring the flashlight are done by the two fast guys and take a total of minutes:
The total time crossing back and forth is minutes + minutes = minutes
