A child is running on a moving sidewalk in an airport. When she runs against the sidewalk's motion, she travels 60 ft in 15 seconds.

Question

A child is running on a moving sidewalk in an airport. When she runs against the sidewalk's motion, she travels 60 ft in 15 seconds. When she runs with the sidewalk's motion, she travels 90 ft in the same amount of time. What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk?

Answer 1

distance = rate*time

 

rate against sidewalk = 60/15 = 4 ft/sec

rate with sidewalk = = 90/15 = 6 ft/sec

 

Let c = child's running rate

Let s = rate of sidewalk

 

c + s = 6

c - s = 4

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2c = 10

c = 5

s = 1

 

The child moves 5 ft/second

The sidewalk moves 1 ft/second