Question 930651: A child is running on a moving sidewalk in an airport. When she runs against the sidewalk's motion, she travels
40ft
in
8
seconds. When she runs with the sidewalk's motion, she travels
90ft
in
10
seconds. What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk?
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! A child is running on a moving sidewalk in an airport.
When she runs against the sidewalk's motion, she travels 40ft in 8 seconds.
When she runs with the sidewalk's motion, she travels 90ft in 10 seconds.
What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk?
:
let c = child's normal running rate, (ft/sec)
let w = sidewalk moving rate
then
(c-s) = effective rate running against the sidewalk
and
(c+s = effective rate running with the sidewalk
:
Write two distance equations, one for each way, dist = rate * time
8(c-s) = 40
10(c+s)= 90
simplify, divide the 1st eq by 8, the 2nd by 10 and we have
c - s = 5
c + s = 9
---------- addition eliminates s, find c
2c = 14
c = 14/2
c = 7 ft/sec is the child's running speed
Find s
7 + s = 9
s = 9 - 7
s = 2 ft/sec, is the rate of the sidewalk
:
:
See if this checks out in the 1s original equation
8(7 - 2) = 40
8(5) = 40
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