Answer to Question #326298 in Algebra for Shang

Question

3.Four men are walking late at night. Together they have one flashlight with a weak battery, so that it can only light the immediate vicinity. They come to a bridge, which is so rickety that only two can cross at the same time. Thus, in order to get to the other end of the bridge, two must cross with the flashlight and one must walk back across the bridge to return the flashlight (they cannot risk throwing it), until all are over. The men can walk at different maximum rates. The slowest needs 10 minutes to cross the bridge, the next 5 minutes, the next 2 minutes and the quickest 1 minute. When two walk together, they must proceed at the pace of the slower. They need to get everyone across the bridge in 17-minutes. Can they do it? How?

Answer 1

At first goes mens: 1 min and 2 min. It takes 2 min.

Back goes men 1 min.

Total it is 3 min.

Then goes men 5min and 10 min. It takes 10 min.

Back goes men 2 min.

Total: 15 min

And in the and goes mens: 1 min, 2 min. It takes 2 min.

Total 17 min.