Fishermen can use echo sounders to locate schools of fish and to determine the depth of water beneath their vessels. An

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Fishermen can use echo sounders to locate schools of fish and to
determine the depth of water beneath their vessels. An ultrasonic
pulse from an echo sounder is observed to return to a boat after
0.200 s. What is the sea depth beneath the sounder? The speed of
sound in water is 1.53 × 103 m s−1 .
(a) 612 m (b) 306 m (c) 153 m (d) 76.5 m
Continuing from the previous question, a school of fish swim
directly beneath the boat and result in a pulse returning to the
boat in 0.150 s. How far above the sea floor are the fish
swimming?
(a) 5480 m (b) 742 m (c) 115 m (d) 38.3 m