Four Kids Bridge Crossing Puzzle | MindYourLogic Bridge Crossing Puzzle

Four kids need to cross a narrow bridge at night using only one lantern. Each kid has a different crossing speed, and the lantern must be carried back and forth. The goal is to find the minimum total time required for all four kids to cross the bridge, which is 21 minutes. This puzzle requires careful planning to optimize the crossing times while managing the lantern efficiently.

Conditions:

Kid A: 1 minute
Kid B: 4 minutes
Kid C: 6 minutes
Kid D: 8 minutes

Objective:
Determine the minimum time required for all four kids to cross the bridge.

Steps to Cross the Bridge in Minimum Time:

First Crossing:

Kid A (1 minute) and Kid B (4 minutes) cross the bridge together.
Time taken: 4 minutes (the time of the slower kid, Kid B).

Lantern Return:

Kid A (1 minute) returns with the lantern.
Time taken: 1 minute.
Total time elapsed: 5 minutes.

Second Crossing:

Kid C (6 minutes) and Kid D (8 minutes) cross the bridge together.
Time taken: 8 minutes (the time of the slower kid, Kid D).

Lantern Return:

Kid B (4 minutes) returns with the lantern.
Time taken: 4 minutes.
Total time elapsed: 17 minutes.

Final Crossing:

Kid A (1 minute) and Kid B (4 minutes) cross the bridge together again.
Time taken: 4 minutes (the time of the slower kid, Kid B).
Total time elapsed: 21 minutes.

Conclusion:
By following this strategy, all four kids will cross the narrow bridge in a total of 21 minutes. The strategy effectively manages the lantern and balances the crossing times of the kids to achieve the minimum total crossing time.