689. While navigating in fog off a coastline of steep cliffs, you hear the echo of the ships fog horn 2 1/2 seconds after the signal was sounded. What is the distance to the shore?

The echo time of 2.5 seconds represents the round-trip travel time of the sound; therefore, the one-way distance to the cliff is calculated using the speed of sound and half the total time, resulting in a distance of approximately 460 yards.