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Karthik
on
14-Jan-2017 10:53

Mr. X takes 30 seconds to go up by using "moving up" escalator and takes 120 seconds to come down using "moving up" escalator. Find the time to move up when the escalator is standstill.

Options: a)45 b)60 c) 75 d)48

Karthik
on
13-Apr-2014 18:02

Ans: 48 seconds.

Let the speed (steps covered by escalator) of moving up escalator be E steps per sec and the man be X steps per sec.

Let the total num of steps in covering the distance be N.

We need to find N/X (That is when E=0)

N/(X+E) = 30

N/(X-E) = 120

30X+30E = 120X - 120E,

150E = 90X,

5E=3X, E=3x/5.

Using eqn1, N/(X+3x/5) = 30,

N/(8X) = 6,

N/X = 48

Let the speed (steps covered by escalator) of moving up escalator be E steps per sec and the man be X steps per sec.

Let the total num of steps in covering the distance be N.

We need to find N/X (That is when E=0)

N/(X+E) = 30

N/(X-E) = 120

30X+30E = 120X - 120E,

150E = 90X,

5E=3X, E=3x/5.

Using eqn1, N/(X+3x/5) = 30,

N/(8X) = 6,

N/X = 48

Divya
on
12-Mar-2016 11:32

Ans: 48 seconds.
Let the speed (steps covered by escalator) of moving up escalator be E steps per sec and the man be X steps per sec.
Let the total num of steps in covering the distance be N.
We need to find N/X (That is when E=0)
N/(X+E) = 30
N/(X-E) = 120
30X+30E = 120X - 120E,
150E = 90X,
5E=3X, E=3x/5.
Using eqn1, N/(X+3x/5) = 30,
N/(8X) = 6,
N/X = 48