# A man standing between two cliffs hears the first echo of a sound after 2 sec and the second echo 3 sec after the initial sound.

Q: A man standing between two cliffs hears the first echo of a sound after 2 sec and the second echo 3 sec after the initial sound. If the speed of sound be 330 m/s, the distance between the two cliffs should be:

(a) 1650 m

(b) 990 m

(c) 825 m

(d) 660 m

Ans: (c)

Sol:speed of sound v = 330 m/s

Let d = distance between two cliffs

and x = distance of man from first cliff then distance of man from 2nd cliff = d-x

$\large \frac{2x}{v} = 2$ …(i)

$\large \frac{2(d-x)}{v} = 3$ …(ii)

On solving we get ,

d = 825 m