Question

John steps on an escalator to leave a subway. Then, 5 seconds later, Jane steps on a parallel escalator to enter the subway. They pass 15 seconds after that. If both escalators are travelling at a speed of 6 feet per second, what is the length â„“ of the escalators

Answer 1

`L = 210 ft`

Step-by-step explanation:

velocity of the Escalators is given as 6 ft/s

now we know that Jane steps on parallel escalator after t = 5 s

so distance moved by John in same time interval is given as

`d = v t`

`d_1 = 6 * 5`

`d_1 = 30 ft`

now John and Jane will move towards each other with relative speed

`v_r = 6 + 6 = 12ft/s`

Then will approach towards each other with this relative speed and meet after t = 15 s

so the distance moved by them

`d = v_r * t`

`d_2 = 12 * 15`

`d_2 = 180 ft`

so total length of the escalators is given as

`L = d_1 + d_2`

`L = 30 + 180`

`L = 210 ft`