A ship sends out a pulse of sound and receives an echo back one second later. If the water is 750m deep, what is the speed of sound in water?

1500 m/s

Explanation:

The sound wave travels 750 meters from the ship to the bottom of the water, then 750 meters back to the ship. So it travels a total distance of 1500 meters in 1 second.

So the average speed is:

v = 1500 m / 1 s

v = 1500 m/s