If the flash-to-bang count is 15, how far is the lightning?

To determine how far away lightning is based on the flash-to-bang count, one commonly used guideline is that for every five seconds counted between seeing the flash of lightning and hearing the thunder (the bang), the lightning strike is approximately one mile away. This rule is based on the difference in speed between light and sound; light travels much faster than sound.

In this case, a count of 15 seconds between the flash and the bang suggests that the lightning is about three miles away. This is calculated by dividing the total seconds by five (15 seconds ÷ 5 seconds per mile = 3 miles). Therefore, the answer that reflects this calculation is appropriate. Understanding this principle allows individuals to measure the distance of lightning strikes accurately, which is vital for safety during storms.