A girl drops a stone into a mine shaft 122.5m deep. How soon after she drops it does she here the sound of it striking the bottom of the shaft?

Answer 1

time elapsed=timefalling+timesound
In both cases, the distance fell is the same.

time falling: 122.5=1/2 g t^2 solve for t.
time sound= distance/speedsound get the speed of sound, figure time sound.

Add the two times.