Subject: General Aptitude · Chapter: Time and Distance · Exam: · Marks: · Difficulty:
A man can walk up a 'moving-up' escalator in 30 seconds. The same man can walk down this 'movingup' escalator in 90 seconds. Assume that his walking speed is same upwards and downwards. How muchtime will he take to walk up the escalator, when it is not moving?
(a)30 sec
(b)45 sec
(c)60 sec
(d)90 sec
Answer
Answer (as printed): B
Explanation
Suppose the escalator has $n$ steps. Let man's speed be $x$ steps per sec. and the speed of the escalator be $y$ steps per sec. Then, $x+y=\frac{n}{30}$ and $x-y=\frac{n}{90}$. Adding, we get: $2x=\frac{n}{30}+\frac{n}{90}=\frac{4n}{90}=\frac{2n}{45}$ or $x=\frac{n}{45}$. $$\therefore \text{Required time} = \frac{n}{(n/45)} = 45\text{ sec}.$$
Explanation as extracted from the printed page; notation may be imperfect.