Crossing The Bridge

Four friends Rajeev, Ramana, Rajesh and Ranjit needs to cross the bridge in exactly 17 minutes in order to see the movie which starts exactly in 17 minutes. All of them are on this side of the bridge. You need to help them across to the other side.

It is a no moon night and there are no lights either on the bridge or anywhere near by. Luckily, they have one flashlight. But, only two people can cross the bridge at one time. It is impossible to cross the bridge without the flashlight. Since they have only one flashlight, it must be walked back and forth and it cannot be thrown. Interestingly, each of them walk at a different speed. When two people are crossing the bridge, they should walk together at the rate of the slower man's pace.

Ranjit needs 10 minutes to cross the bridge.
Rajesh needs five minutes to cross the bridge.
Ramana can cross the bridge in 2 minutes.
Rajeev participated in walking race, and he can cross the bridge in one minute.

For example: If Rajeev and Ranjit walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Ranjit then returns with the flashlight, a total of 20 minutes have passed and you have failed the mission. Your goal is to get all four friends across in 17 minutes or less.

Answer to the Puzzle

Rajeev (1 min) and Ramana (2 min) walk across first bringing the total to 2 minutes. Then Rajeev (1) walks the flashlight back, total 3 minutes. Rajesh (5) and Ranjit (10) walk across, total 13 minutes. Ramana (2) walks the light back, total 15 minutes. Ramana (2) and Rajeev (1) walk across, total and answer 17 minutes.

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