Preeti reached the metro station and found that the escalator was not working. She walked up the stationary escalator in time `t_1`. On other days, if the remains stationary on the moving escalator, then the escalator takes her up in time `t_2`. The time taken by her to walk up on the moving escalator will be :

Options

A. `(t_(1) t_(2))/(t_(2) - t_(1))`
B. `(t_(1) t_(2))/(t_(2) + t_(1))`
C. `t_(1) - t_(2)`
D. `(t_(1) + t_(2))/(2)`

Explanation

Let `d` : height of escalator
Stationary escalator : `t_(1) = dlv`
Moving escalator : `t_(2) = d//u`
Moving Preeti on moving escalator
`t = (d)/(v + u) = (d)/((d)/(t_(1)) + (d)/(t_(2))) = (t_(1) t_(2))/(t_(1) + t_(2))`