Question

When Kelsey is not on the moving sidewalk, she can walk the length of the sidewalk in 3 minutes. If she stands on the sidewalk as it moves, she can travel the length in 2 minutes. If Kelsey walks on the sidewalk as it moves, how many minutes will it take her to travel the same distance? Assume she always walks at the same speed.

Answer 1

1.2 minutes

Explanation:

Kelsey moves 1/3 length per minute. The sidewalk moves 1/2 length per minute. Walking on the sidewalk, Kelsey moves (1/3+1/2) = 5/6 lengths per minute, or 6/5 minutes per length.

So it takes Kelsey 1 1/5 minutes to walk the length on the moving sidewalk.