Echo distance from round-trip sound travel

Steps:

• Sound travels to cliff and back, so total distance = 2 × ship-to-cliff distance (d).
• Total time for round trip = 4.0 s.
• Speed of sound = 320 m/s, so total distance = speed × time = 320 × 4 = 1280 m.
• Ship-to-cliff distance d = 1280 / 2 = 640 m.

Why B is correct:

• B (640 m) matches the formula for echo distance: d = (v × t)/2, where sound completes a round trip at constant speed.

Why the others are wrong:

• A: 160 m ignores the round trip, treating time as one-way only.
• C: 1280 m uses total round-trip distance without halving for one-way to cliff.
• D: 2560 m doubles the total distance erroneously, perhaps confusing with twice the round trip.

Final answer: B