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 remaines stationary on moving esclalator, then the escalator takes her up in time t 2 . The time taken by her to walk up on the moving escalator will be 1) t 1 + t 2 / 2 2) t 1 t 2 /t 2 - t 1 3) t 1 t 2 / t 2 + t 1 4) t 2 - t 1 Now I have solved the question and I am getting answer (2) but answer is (3) as shown is attachment . Dont relative velocities of two body moving in same direction is found out by subtraction.? Please explain.

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 remaines stationary on moving esclalator, then the escalator takes her up in time t₂. The time taken by her to walk up on the moving escalator will be

 

1) t₁ + t₂ / 2

2) t₁t₂/t₂ - t₁

3) t₁t₂ / t₂ + t₁

4) t₂ - t₁
 

Now I have solved the question and I am getting answer (2) but answer is (3) as shown is attachment . Dont relative velocities of two body moving in same direction is found out by subtraction.?

 

Please explain.