Question

A boy standing 70 metre from a high Wall claps his hands.After how much time is an echo heard?(the speed of sound in air is 350ms )

Answer 1

After 0.01 sec he will hear echo.

HOPE THIS WILL HELP U

Answer 2

so it takes a double time from reaching the distance to our ears

now we find the time taken to reach there

v=d/t


350 = 70/t

t=70/350 = 1/5 = 0.2sec

since it takes double time

0.2×2=0.4sec