Question 464651
The speed of sound and water is about 1500m/sec. If a receiver on a ship receives an echo from the bottom 3 seconds after it is transmitted then the depth of the ocen is ----- meters? 
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The speed of sound in water, right?
It takes 3 seconds to travel to the bottom, then back to the ship.
1500 m/sec * 3 sec = 4500 meters round trip
depth = 4500/2 = 2250 meters.
Make sense?
1.5 seconds to the bottom, 1.5 seconds back to the ship