SOLUTION: A girl walks down a moving subway escalator. It takes her one minute to go from the street level to the subway platform. If she has walked twice as fast as before, it would take he
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Question 898499: A girl walks down a moving subway escalator. It takes her one minute to go from the street level to the subway platform. If she has walked twice as fast as before, it would take her 45 seconds to go down. How long will it take her standing on the escalator? Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! A girl walks down a moving subway escalator.
It takes her one minute to go from the street level to the subway platform.
If she has walked twice as fast as before, it would take her 45 seconds to go down.
How long will it take her standing on the escalator?
let d the length of the escalator in ft
let s = effective speed the first time
then
2s = effective speed the 2nd time
let x = the speed of the escalator
:
1st scenario = 60 sec
d = 60(s+x)
2nd scenario = 45 sec
d=d, therefore
60(s+x) = 45(2s+x)
simplify divide by 15
4(s+x) = 3(2s+x)
4s + 4x = 6s + 3x
4x - 3x = 6s - 4s
x = 2s, the speed of the escalator
:
To find s, let's assume the d = 180 ft
60(s+2s) = 180
60(3s) = 180
180s = 180
s = 1 ft/sec
:
we know the escalator is 2s, or 2 ft/sec
Find the time it takes just standing on the escalator = 90 seconds
:
:
Confirm this, the 2nd run is 4s or 4 ft/sec
180/4 = 45 sec
