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

Answer:

$L = 210 ft$

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

$d = v t$

$d_1 = 6 \times 5$

$d_1 = 30 ft$

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

$d = v_r \times t$

$d_2 = 12 \times 15$

$d_2 = 180 ft$

so total length of the escalators is given as

$L = d_1 + d_2$

$L = 30 + 180$

$L = 210 ft$