SOLUTION:
A child is running on a moving sidewalk in an airport. When he runs against the sidewalk's motion, he travels 32ftin 8 seconds. When he runs with the sidewalk's motion, he travel
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A child is running on a moving sidewalk in an airport. When he runs against the sidewalk's motion, he travels 32ftin 8 seconds. When he runs with the sidewalk's motion, he travel
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Question 1114406:
A child is running on a moving sidewalk in an airport. When he runs against the sidewalk's motion, he travels 32ftin 8 seconds. When he runs with the sidewalk's motion, he travels 120ftin 12 seconds. What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk? Answer by ikleyn(52855) (Show Source):
Let u be the child's own speed in ft/s, and
let v be the moving sidewalk speed.
The child's effective velocity running with he sidewalk's motion is
u + v = 120/12 = 10 ft/s
The child's effective velocity running against he sidewalk's motion is
u - v = 32/8 = 4 ft/s
Again
u + v = 10
u - v = 4
-------------------------Add the equations to exclude v
2u = 10 + 4 = 14 ====> u = 7 ft/s.
Then v = 10-u = 10-7 = 3 ft/s.
Answer. The child own speed is 7 ft/s. The running sidewalk speed is 3 ft/s.
