escalator

Question

Ajay walked down a descending escalator. He took 60 steps and reached the bottom in 60 sec. On another occasion he took 80 steps and reached the bottom in only 50 sec. Find the number of steps in escalator.

(a) 160  (b) 180

(c) 200  (d) 240

Answer 1

I made comparison with boat stream problem.Considered elevator as river,the man as a boat .

Distance:steps,Speed:steps per second,

60 steps in 60 sec=1 sps [StepPerSec]

80 steps in 50 sec=8/5 sps

Speed1 s1 would be (1sps +e) [Considered elevator speed as e sps,added since its downstream]

Speed2 s2 would be (8/5sps +e)

In the above distance is constant so s1*t1=s2*t2  so s1/s2=t2/t1.We solve this equation we get e=2 sps

Now total distance=elevator steps= s1 * t1 =(1 sps + 2sps) * 60 = 3*60 = 180.