Riddle Me This: Bridge Crossing
Test your skills of deduction with the March 2022 edition of Riddle Me This: Bridge Crossing
Alan, Bob, Cal, and Dan are all on one side of a narrow and danaerous bridge that they would like to cross. It is late at night and very dark so they cannot cross safely without a flashlight. They have only one flashlight and the bridge is only strong enough to support the weight of two people at once. Each of the four people walk at different speeds:
- Alan can cross the bridge in one minute
- Bob can cross in two minutes
- Cal can cross in five minutes
- Dan can cross in ten minutes
- When two people are walking together sharing the flashlight they walk at the slower person’s pace
How quickly can Alan, Bob, Cal, and Dan all get across the bridge safely?
Click to Reveal Answer
Alan and Bob cross in 2 minutes, Alan returns with the flashlight in 1 minute, Cal and Dan cross in 10 minutes, bob crosses with the flashlight in 2 minutes, Alan and bob cross in 2 minutes. Total time 17 minutes.
19 minuter
19 minutes
19 min
19 minutes
19 minutes
19 minutes, assuming the flashlights beam will not span half the bridge.
18 minutes if the flashlights beam spans half the bridge.
19 minutes
A.P. I like you flashlight spanning half bridge.
Dan and Cal go to middle of bridge and Dan continues to far end (10min)
Alan crosses (+1=11min)
Bob goes to middle of bridge (+1=12min)
Bob and Cal continue to far end of bridge (+2.5min=14.5min)