The Collapsing Bridge Puzzle
 | A bridge will collapse in 17 minutes. |
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 minutes
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!
Ashwyn Sam kindly provided us with an alternative solution:
A and B cross first using up 2 minutes
B comes back making it 4 minutes
C and D cross making it 14 minutes
then A crosses back over making it 15 minutes
And finally A and B cross together, also for a total of 17 minutes.