What depth does the echo sounder indicate in the given scenario?

• A. 39 feet
• B. 12 feet
• C. 27 feet
• D. 0 feet

Answer: (C)

The main idea is that an echo sounder tells you the vertical distance from the transducer to the seabed by timing how long it takes for a sound pulse to travel to the bottom and back. This two-way travel time, combined with the speed of sound in water, is converted into a depth reading. So the value you see on the screen is the depth of the water directly beneath the boat.

In the scenario, the bottom is positioned at a distance of 27 feet below the transducer, so the echo sounder displays 27 feet. If the bottom were closer, the reading would be a smaller number (like 12 feet); if farther, a larger number (like 39 feet); and if the bottom were right at the transducer, it would show 0 feet. Thus, 27 feet matches the bottom’s actual position shown in the scene.