Burn the Bridge
Four adventureres are being chased by a tribe of savages. They come to a very old rope bridge which crosses a ravine. They determine they have a 17 minute advantage over their pursuers. The rope bridge is weak and will only support 2 people at a time. To further complicate matters, it is dark and each crossing will require use of their only flashlight, to insure good footing. The bridge is too wide to allow the flashlight to be thrown across. The 4 adventurers, being of different age and levels of fitness, move at different speeds.
Adventurer A can cross the bridge in 10 minutes
Adventurer B can cross the bridge in 5 minutes
Adventurer C can cross the bridge in 2 minutes
Adventurer D can cross the bridge in 1 minute
How do all 4 adventurers get across the bridge in 17 minutes? ... so they can set fire to the bridge and assure their safety from the savages.
(amendment: when 2 adventurers are crossing together, they can move only as fast as the slower one)
Adventurer A can cross the bridge in 10 minutes
Adventurer B can cross the bridge in 5 minutes
Adventurer C can cross the bridge in 2 minutes
Adventurer D can cross the bridge in 1 minute
How do all 4 adventurers get across the bridge in 17 minutes? ... so they can set fire to the bridge and assure their safety from the savages.
(amendment: when 2 adventurers are crossing together, they can move only as fast as the slower one)
posted by Zaux at
9:09 AM
8 Comments:
the obvious question is:
with such varying speeds of travel, how were they able to gain a 17 minute advantage over their pursurers ... I concede the point and agree ... let's suspend our disbelief and find a solution... ;)
added an amendemnt to clarify crossing speeds
Person D holds the flashlight the entire time.
C and D go across together (2 minutes)
D goes back (2+1= 3 minutes)
B and D go across together (3+5= 8 minutes)
D goes back (8+1= 9 minutes)
A and D will cross the bridge with the natives 8 minutes behind them. By the time the natives reach them they will already be almost across the bridge so it won't matter.
Posted by The Godson
Hi Godson ...
your solution has the adventurers completing the crossing in 19 minutes ... there is a solution whereby they cross in 17 minutes
hi guys ...
I will be gone for the next 3 to 4 hours ... upon return, I will read and enjoy your solutions, and post the publish one
C+D cross, 2mins
D returns, 1min
A+B cross, 10min
C returns, 2min
C+D cross, 2mins
Total 17 mins
regards, Curtis
Hi Curtis ...
you got it ... good job
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