Final answer:
To determine the time before you hear the sound of thunder after a lightning strike 3 km away, divide the distance by the speed of sound (0.388 km/s), resulting in approximately 7.7 seconds after rounding to the nearest tenth.
Step-by-step explanation:
In a thunderstorm, when lightning strikes the ground 3 km away from you, and if we are given the speed of sound is 0.388 km/s on a hot day, we can calculate the time it takes for the sound to reach you using the formula: Time = Distance Speed. To calculate the time it will take to hear the thunder after seeing the flash of lightning, divide the distance (3 km) by the speed of sound (0.388 km/s). The calculation is as follows: Time = 3 km 0.388 km/s = 7.732 s. Rounding to the nearest tenth of a second gives us approximately 7.7 seconds that will elapse before you hear the sound of thunder.