Four friends A, B, C, D
Need to cross a bridge..
A maximum of 2 people can cross at a time..
It is night and they have just 1 lamp.
People that cross the bridge must carry the lamp to see the way..
A pair must walk together at the speed of slower person…
Speeds of
A: 1 minute to cross bridge
B: 2 minutes to cross bridge
C: 5 minutes to cross bridge
D: 10 minutes to cross bridge
Now question is… “what is the total minimum time required by all 4 friends to cross the bridge….?
See Solution : BridgePerson A : 1 minute
Person B : 2 minutes
Person C : 5 minutes
Person D : 10 minutes
Person C and D are the slowest guys, if they don’t walk together that it self will make it 15 minutes, In this case (the best way to save time is) :
Initially A,B,C,D ========
First A& B will cross the bridge and A will come back => time taken 2 + 1 => 3
A,C,D ======== B
Now C & D should cross the bridge together and B will come back => time taken 10 + 2 => 12
Now A & B will cross the bridge together => time taken 2
total time 3 + 12 + 2 => 17
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