Question

"John fires a gun towards a hill and hears its echo after 5 seconds. He then
moves 320 m towards the hill and fires his gun again. This time he hears the
echo after 3 seconds. Calculate the velocity of sound. "

Answer 1

Given :
Time=5 sec
Let d be the distance between John and the hill at the begining.
 V = 2d/t
=2d / 5 ---------- equ (1)
He then moves 320m towards hill. 
Therefore distance is (d-320 )m
Therefore V=2(d-320)/2 ---------- equ (2)
Since velocities are same
 2d/5 = 2(d-320)/3
6d=10d-3200
4d=3200
d=800m
Velcoity =V=2x800/5=320 m/s

Answer 2

ANSWER IS IN THE IMAGE