An echo is return

Given

Speed of sound (u) = 342 m/s

Time taken for hearing the echo (t) = 6 s

Now

In 6s, sound has to travel twice the distance between the source and reflecting surface. Therefore, the distance of the reflecting surface from the source is 2052/2 = 1026 m

OR

Given

Speed of sound (u) = 346 m/s

Time taken for hearing the echo (t) = 4s

Now

Now

In 4 s, sound has to travel twice the distance between the cliff and aditi. Therefore, the distance between the cliff and aditi is 1368/2 = 684 m