A splash is heard 3.12s after a stone is dropped into a well 45 m deep. The speed of sound in air is [g = 10 ms^-2]

Time taken by stone to reach the water surface t₁ ​= $\sqrt{2h/g}$ ​

put h =45 and g = 10 m/s²

t₁ = 3 s

So time taken by sound to reach the top of the well 45m above the water surface is t−t₁​ = 3.12 − 3 = 0.12s

So the speed of sound in air distance/time = 45/0.12 = 375 m/s