Crossing the Bridge Puzzle: A bridge will collapse in 17 minutes.
4 people want to cross it before it will collapse. It is a dark night and there is only one torch between them.
Only two people can cross at a time.
“A” takes a minute to cross.
“B” takes 2 minutes.
“C” takes 5
and “D” takes 10 minutes
How do they all cross before the bridge collapses?
A and B cross first using up 2 minutes.
A comes back making it 3
C and D cross making it 13 minutes
then B crosses back over making it 15 minutes.
And finally A and B cross together to make it 17 minutes!
Detailed Solution to the problem is as follows:
|Move||Trip Time||Total Time|
|A & B Cross with torch||2||2|
|A Return with torch||1||3|
|C & D Cross with torch||10||13|
|B Return with torch||2||15|
|A & B Cross with torch||2||17|