Question

a man walks up a stationary escalator in 90sec. when this man stands on moving escalator he goes up in 60 sec. the time takes by the man to walks up the moving escalator is

Answer 1

Final Answer :36s

1)Let
v = walking speed of person
u= escalator speed
Let the length of escalator be 'L'.
The person walks up the stationary escalator in 90s.
L = 90 v => v = L/90

2)The escalator moves a distance L in 60s.
L = 60u
=> u = L/60.

3)When walking up the moving escalator , the net speed = v + u

Time taken = L / (v + u) = L/ (L/90+ L/60)
= 36s.

Answer 2

Answer:

36 s

Explanation:

let u=man walks @stationary

v= man stands @ moving

d be distance

man walks @90 seconds

i.e d=90u

u=d/90

man walks in 20 seconds

i.e d=60v

v=d/60

net speed=d/v+u

i.e. = d/d/60+d/90

=36 seconds

Hope this answer help you