Question

A man can walk up a moving 'up' escalator in 30 s. The same man can walk down this moving 'up' escalator in 90 s. Assume that his walking speed is same upwards and downwards. How much time did he take to walk up the escalator, when it is not moving? (1995)

• A. 30s
• B. 45s
• C. 60s
• D. 90s

Answer 1

The correct option is B 45s

Let the speed of escalator be y ft per second speed of man's be x ft per second .Let us assume that length of the escalator be 90 ft.
Then, $x+y=\frac{90}{30}\to x+y=3............\left(i\right)$

And $x-y=\frac{90}{90}\to x-y=1..................\left(ii\right)$

$\to$ x=25 ft/sec.And time taken by the man to walk up bt the escalator when it is not moving $=\frac{90}{2}=45$ second.

Also note : Options a and d can directly be eliminated.