A boy hears his own echo from a distant hill after 0.8 s. [[1]] is the distance from hill, if the speed of sound in air is 340m/s.

A boy hears his own echo from a distant hill after

0.8 s

136 m

is the distance from hill, if the speed of sound in air is

340 m / s

.
It is given that the time taken by the echo to return is

0.8 s

and the speed of sound in air is

340 m / s

.
The speed of the sound wave is given by distance divided by the time taken.

Distance = speed \times time

= 0.8 \times 340

= 136 m

Hence, the distance from the hill is

136 m

A boy hears his own echo from a distant hill after $0.8 s$ . [[1]] is the distance from hill, if the speed of sound in air is $340 m / s$ .