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Preeti reached the metro station and fou...

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 she remains stationary on the moving escalator takes her up in time `t_2`. The time taken by her to walk up on the moving escalator will be:

A

`(t_1t_2)/(t_2-t_1)`

B

`(t_1t_2)/(t_2+t1)`

C

`t_1-t_2`

D

`(t_1+t_2)/2`

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