Bridge Over Troubled Students

There are four men who want to cross a bridge. They all begin on the same side. You have 17 minutes to get all of them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either one or two people, must have the flashlight with them. The flashlight must be walked back and forth, it cannot be thrown, etc. Each man walks at a different speed. A pair must walk together at the rate of the slower man

Man 1= 1 minute to cross

Man 2= 2 minutes to cross

Man 3= 5 minutes to cross

Man 4= 10 minutes to cross

For example, if Man 1 and Man 4 walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Man 4 returns with the flashlight, a total of 20 minutes have passed, and you have failed the mission.

please i want a answer

Note by Aman Baser
5 years ago

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Let 1,2,3,4 denote Man1,2,3,4 and A,B denote the Sides of the bridge, and @ denote the torch.

1st Step :- 1,2 @ go To B. Time taken so far = 2m

2nd Step :- 2 @ go to A.Time taken so far = 2m+2m=4m.

3rd Step :- 34@ go to B. Time taken so far = 4m+10m=14m.

4th Step :- 1@ go to A.Time taken so far = 14m + 1m = 15m.

5th Step. 21@ go to B. Time taken so far = 14m + 1m = 17m.

ABTime taken
@1234Start
3412@2m
324@12m
2134@10m
21@341m
1234@2m

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agree with you:)

Dinesh Nath Goswami - 5 years ago

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I am not able to understand the answer

Aman Baser - 5 years ago

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Edited. Hope you understand now.

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@Siddhartha Srivastava Thank you

Aman Baser - 5 years ago

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Please give me answer. I am too confused

Aman Baser - 5 years ago

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I used Trial and Improvement.

  1. Man 1 and Man 2 cross (2 minutes)
  2. Man 1 returns (1 minute)
  3. Man 3 and Man 4 cross (10 minutes)
  4. Man 2 returns (2 minutes)
  5. Man 1 and Man 2 cross (2 minutes)

Total Minutes : 17

Sajid Mamun - 4 years, 11 months ago

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