Question 315716: it takes a child 90 seconds to climb the 60 m . length of an escalator which is not working when in operation , the escalator lifts a passenger from bottom to top in 60 seconds . how much long does it take the child to cover the 60 meters, if she walks on the moving escalator ?
(A) 30 sec (B) 36 sec (C) 40 sec (D) 45 sec (E) 50 sec
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! it takes a child 90 seconds to climb the 60 m . length of an escalator which is not working when in operation ,
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Child's rate = 60/90 = 2/3 m/sec
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the escalator lifts a passenger from bottom to top in 60 seconds
Escalator rate = 60m/60sec = 1 m/sec
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. how much long does it take the child to cover the 60 meters, if she walks on the moving escalator ?
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Rate of child and escalator together:
(2/3) + 1 = 5/3 m/sec.
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Time for child to move 60 meters on the moving escalator:
time = distance/rate = 60 m/[(5/3)m/sec] = 12*3 sec = 36 sec
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Cheers,
Stan H.
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(A) 30 sec (B) 36 sec (C) 40 sec (D) 45 sec (E) 50 sec
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