Its dark in the night and they have only one torch with them.They can not walk on the bridge without the torch.to make the matters worse the bridge can support only a maximum of two persons at any given time.
the time taken by A,B,C,D individually to cross the bridge is given below
A takes 1 min to cross the bridge
B takes 2 min to cross the bridge
C takes 5 min to cross the bridge
D takes 8 min to cross the bridge
if two of them travel together the faster one has to adjust his speed according to the slower one so that they can share the torch.
what is the minimum time taken by them to cross the bridge?
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Solution: Correct answer is given by guru.
First Trip:A+B crosses the bridge and A comes back- Total time taken for this trip =2+1
Second Trip:C+D cross the bridge and B comes back-Total time taken for this trip=8+2
Final Trip :A+B Again -Total time taken for this trip=2
Total time taken for the all of them to cross: 3+10+2= 15
My take ...
ReplyDelete1) A and B cross the bridge together and A comes back: 2 + 1 = 3 mins
2) A and C cross together and A comes back : 5 + 1 = 6 mins
3) A and D cross together: 8 mins
total = 3 + 6 + 8 = 17 mins.
A & B goes together first so that duration for this trip is 2 minutes.
ReplyDeleteA comes back, for this trip 1 minute
C and D will go together, for this trip 8 minutes.
B comes back, for this trip 2 minutes.
A and B goes together for this trip 2 minutes.
Total = 2 + 1 + 8 + 2 + 2 = 15 Minutes