Question

A group of four people has to cross a bridge. It is dark, and they have to light the path with a flashlight. No more than two people can cross the bridge simultaneously, and the group has only one flashlight. It takes different time for the people in the group to cross the bridge:

Chris crosses the bridge in 1 minute,

Tracy crosses the bridge in 2 minutes,

Ashley crosses the bridge in 5 minutes,

Jalen crosses the bridge in 10 minutes.



How can the group cross the bridge in 17 minutes?

Answer 1

Explanation:

Only two people can cross the bridge at the same time.

Chris takes 1 minute, Tracy takes 2 minutes, Ashley takes 5 minutes, Jalen takes 10 minutes.

Step 1: To make sure they all cross before 17 minutes is exceeded.

First, send Chris (the fastest) and Jalen (the slowest) together.

17 - 1 = 16

Chris crosses in 1 minute, Jalen, is still crossing (9 minutes left). 16 minutes left in all.

Next, Ashley crosses the bridge (5 minutes)

16 - 5 = 11

Ashley crosses with 11 minutes left, Jalen still has 4 minutes left, 11 minutes left in all.

Finally, Tracy crosses. Jalen would finish his crossing (4 minutes left). 11 minutes left in all.

11 - 4 = 7

The whole group costs with 7 minutes left in all

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