Back to Logic Problems
Bridge and Torch Problem
This Hard puzzle in the “logic” category rewards careful reading and step-by-step reasoning. Use the hint if you are stuck, then compare your approach with the explained answer.
Four people need to cross a narrow bridge at night. They have only one torch, and at most two people can cross at a time.
Each person walks at a different speed:
- Person A: 1 minute
- Person B: 2 minutes
- Person C: 7 minutes
- Person D: 10 minutes
When two people cross together, they must walk at the speed of the slower person.
The torch must always be carried, so someone must bring it back if needed.
What is the minimum time required for all four to cross the bridge?
Preparing…