The speed of sound in air is approximately 340 m/s. The speed of light in air is approximately 3 x 108 m/s. If 10 seconds elapses between seeing a lightning strike and hearing the thunder, how far away was the lightning strike?

3400 m

Explanation:

Both lightning and thunder happen at the same time but one is faster than the other. The distance traveled by a sound can be calculated from its speed such that;

 speed = distance/time, hence, distance = speed x time.

For a thunder with 340 m/s speed and 10 seconds away from lightning, the distance between the thunder and the lightning can be calculated as;

distance = 340 m/s x 10 s = 3400 m