Four people cross a bridge at night with one torch. The bridge holds two people at a time. Their crossing times are 1, 2, 5 and 10 minutes, and pairs walk at the slower speed. What's the fastest total time?
Hint: Send the two slowest across together.
17 minutes.
1 and 2 cross (2). 1 returns (1). 5 and 10 cross (10). 2 returns (2). 1 and 2 cross (2). Total: 2+1+10+2+2 = 17.
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