What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk?

Question

A child is running on a moving sidewalk in an airport. When she runs against the sidewalk's motion, she travels
60ft
in
10
seconds. When she runs with the sidewalk's motion, she travels
130ft
in
13
seconds. What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk?

Answer 1

This is a speed = distance/time problem.

 

 

Let u = the child's speed and v = the speed of the moving sidewalk.

 

 

60/10 = 6 = v - u  when the child is running in the opposite direction.

 

130/13 = 10 = v + u  when the child is running in the same direction.

 

 

Adding the two equations,

 

16 = 2v or v = 8 ft/s

 

So, u = 2 ft/s from either equation.