Answer:
2,250 meters deep
Explanation:
If the time taken for the the signal to return to the boat means that it took 3 seconds for the signal to travel to and from the floor the same distance. That means it took 1.5 seconds to travel to the floor at a speed of 1500m/s means that it is 1500 multiplied by 1.5 to a distance of 2,250m. (Derived from the speed = distance divided by time formula to distance = speed multipled by time)
