Question

A mountaineer shouts for help. Half a second later she hears the echo. How far away is the rock which is reflecting her voice? (Speed of sound in air = 330 m/s.)

Answer 1

Speed of sound in air = v = 330 m/s
Time (t) it took for the mountaineer to hear her echo = (1/2) sec
Let us assume that the distance between the mountaineer and the rock was d.
Distance = Speed $\times$ Time
2d = v $\times$ t
2d = 330 $\times$ (1/2)
d = 330 / 4 = 82.5 m
Thus, the rock that reflected her voice was 82.5 m away from her.