There are four people who want to cross a rickety bridge; they all begin on the

Q: There are four people who want to cross a rickety bridge; they all begin on the

Times: 1st crossing: (1) with (9). Time 9 minutes. Times: 2nd crossing: (1 alone). Time 1 minute. Times: 3rd crossing: (1) with (8). Time 8 minutes. Times: 4th crossing: (1 alone). Time 1 minute. Times: 5th crossing: (1) with (4). Time 4 minutes. Total Time: (9 + 1 + 8 + 1 + 4 ) = 23 minutes.

ID: 648340 • Letter: T

Question

There are four people who want to cross a rickety bridge; they all begin on the same side. Your object is to get them all across to the other side in the minimum amount of time. It is night and they have one flashlight. A maximum of two people can cross the bridge at one time. Any party that crosses, either one or two people, must have the flashlight with them. The flashlight must be walked back and forth; it cannot be thrown, for example. Person 1 takes 1 minute to cross the bridge; person 2 takes 4 minutes; person 3 takes 8 minutes; and person 4 takes 9 minutes. A pair must walk together at the rate of the slower person

Explanation / Answer

Times: 1st crossing: (1) with (9). Time 9 minutes.

Times: 2nd crossing: (1 alone). Time 1 minute.

Times: 3rd crossing: (1) with (8). Time 8 minutes.

Times: 4th crossing: (1 alone). Time 1 minute.

Times: 5th crossing: (1) with (4). Time 4 minutes.
Total Time: (9 + 1 + 8 + 1 + 4 ) = 23 minutes.

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There are four people who want to cross a rickety bridge; they all begin on the

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