Weekly Mathematics Challenge
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Problem 2, 15/6/2025
The bridge crossing problem
Four people need to cross a narrow, rickety bridge at night. They have one torch, and the bridge is too dangerous to cross without it. At most, two people can cross at a time, and they must move at the slower person's pace when crossing together.
Each person takes a different amount of time to cross:
Person A: 1 minute
Person B: 2 minutes
Person C: 5 minutes
Person D: 10 minutes
What is the fastest time for all four people to get across the bridge?
Constraints:
The torch must be carried on each crossing.
No more than two people can be on the bridge at a time.
When two people cross together, they move at the pace of the slower person.
Get everyone across the bridge in the least amount of time possible.
Each person takes a different amount of time to cross:
Person A: 1 minute
Person B: 2 minutes
Person C: 5 minutes
Person D: 10 minutes
What is the fastest time for all four people to get across the bridge?
Constraints:
The torch must be carried on each crossing.
No more than two people can be on the bridge at a time.
When two people cross together, they move at the pace of the slower person.
Get everyone across the bridge in the least amount of time possible.
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