Time Problem

4 friends A B C D are trying to cross a forest. It takes 2,3,5,7 mins for each of them respectively. But they have only one torch and nothing else. And the condition is that the forest can be crossed only with torch and a maximum of two people can pass by the forest at a time. What will be the minimum time in which the forest can be crossed. (Hint: if A and B go together in a turn then they would take 3 mins as B takes 3).


The answer is 18.

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2 solutions

Siva Renganath
Jul 16, 2014

Here A takes 2 mins , B takes 3 mins , C takes 5 mins and D takes 7 mins to cross the forest.The minimum time in which the forest can be crossed :

1.AB cross - 3 mins

2.A comes back - 2 mins

3.CD cross - 7 mins

4.B comes back - 3 mins

5.AB cross - 3 mins

Therefore the minimum time taken = 3+2+7+3+3 = 18 mins

Prabhat Sharma
Jul 11, 2014

I think ans is 19 3,2 will take 3min 2 min fr reverse cross ,total 5min 2,5 will take 5 min,total 10min Again reverse cross fr 2 min ,total 12min 2,7 will take 7 min ,total 19 min

me too got 19 donno how they get 18 !! Somebody explain !!

Tanmay Rajani - 6 years, 11 months ago

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