Here's another fun math question, and I believe Side Bar may have posed this question some time ago in another context at a Margaret Street BBQ but anyway...
Four people have to get through a dark tunnel with a torch. A maximum of two people can go through at a time, with the torch always being needed to see where you are going (so the carrier of the torch must go each way). The four people have different rates of getting through the tunnel - 10 minutes, 5 minutes, 2 minutes, and 1 minute. What is the minimum number of minutes needed to get all 4 people through the tunnel?
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2 comments:
Best I can do is 19 minutes:
10 and 1 walk through together = 10 minutes, 1 walks back = 1 minute, 5 and 1 walk through together = 5 minutes, 1 walks back = 1 minute1, 2 and 1 walk through together = 2 minutes. 10 + 1 + 5 + 1 + 2 = 19.
Ok. I am down to 17. Duh.
1+2 go through
1 goes back
5+10 go through
2 goes back
1+2 go through
Is there a faster way than 17?
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