Four people need to cross a bridge at night and they have one torch. The bridge can handle the load of only two people at a time. Person **A** can take **10 minutes**, B takes 7 minutes, C takes 2 minutes and D takes 1 minute to cross the bridge. When **two people cross the bridge together**, they must **move at the slower person’s pace**. What’s the minimum time taken by four of them to cross the bridge.

Puzzle Questions

**Solution** –

Time taken by each person

A – 10 Minutes

B – 7 Minutes

C – 2 Minutes

D – 1 Minutes

So we need to calculate the minimum time taken by four of them to cross the bridge.

i) First C and D will go. D comes back with torch.

ii) A and B will go this time. C comes back with torch.

iii) Now C and D will go.

So the total time taken is

i) 2 (slower pace is 2 in case of C and D) + 1 (Time take by D comes back with torch)

ii) 10 (Slower pace is 10 in case of A and B) + 2

iii) 2

If we add three of them, total minimum time taken is 17 Minutes.

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