A person climbs up a stalled escalator in 60s. If standing on the same but escalator running with constant velocity, he takes 40 s. How much time is taken by the person to walk up the moving escalator?

Options

A. 37s
B. 27s
C. 24s
D. 45s

Answer

c

Explanation

Let the total length of the path covered by thee escalator be d meters.
Speed of the person climbing up stalled escalator,
`v_(1)=(d)/(60)m//s`
Speed of the escalator `v_(2)=(d)/(40)m//s`
Let the time taken by the person to walk up the moving escalator be t seconds
Thus, the velocity of the person will be, `v=(d)/(t)` m/s
`v=v_(1)+v_(2)`
`(d)/(t)=(d)/(60)+(d)/(40)`
`(1)/(t)=(2+3)/(120)`
`rArr t=(120)/(5)=24s`.