## Bridge Crossing Puzzle (Interview Puzzle)

###### 3 years ago Lalit Bhagtani 0

**Bridge Crossing Puzzle :-** Four people need to cross a rope bridge to get back to their camp at night. Unfortunately, they only have one flashlight and it only has enough light left for 17 minutes. The bridge is too dangerous to cross without a flashlight, and it’s only strong enough to support two people at any given time. Now each of the campers walks at a different speed. One can cross the bridge in 1 minute, another in 2 minutes, the third in 5 minutes, and the slowest camper takes 10 minutes to cross. How can the campers make it across in exactly 17 minutes? Bridge crossing puzzle …

## Now try to solve this on your own…

## Solution of Bridge Crossing Puzzle :-

Let’s name each camper for easy understanding, A cross the bridge in 1 minute, B cross the bridge in 2 minutes, C cross the bridge in 5 minute and D cross the bridge in 10 minutes.

There are two points, which we have to consider while solving this problem :-

When two campers cross the bridge, the total time taken will be the time of the camper who take the longest to cross the bridge.

Time taken by the camper while returning back to initial point is also added to total time taken.

Let’s solve the problem.

**First Step :-** Two campers, which takes the least time to cross the bridge are send first. In this case, A and B will be sent, So total time taken will be 2 minutes.

C D ————————————- A B

**Second Step :-** Camper, who takes the least time among the campers on another side will be sent back. In this case, A will be sent back, So total time was taken will be 1 minute.

C D A ———————————– B

**Third Step :-** Two Campers, which takes maximum time to cross the bridge are sent second. In this case, C and D will be send, So total time taken will be 10 minutes.

A —————————————- B C D

**Fourth Step (same as the second step) :-** Camper, who takes the least time among the campers on another side will be sent back. In this case, B will be sent back, So total time was taken will be 2 minutes.

A B ————————————– C D

**Fifth Step :-** In the end remaining two campers will be send, In this case, A and B will be send, So total time taken will be 2 minutes.

————————————— A B C D

So Total time take to cross the bridge by 4 campers will be 2 + 1 + 10 + 2 + 2 = 17 minutes

Answer of Bridge Crossing Puzzle :- **17 minutes**

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