A boy yells in a narrow valley. The sound reflects off of a boulder that is 80 m away. How long will it take to hear the echo if the speed of a sound wave is 320 m/s ? open paren speed is equal to distance over time close paren

The sound must travel to the boulder and back, so its total distance is 80 m + 80 m = 160 m. Using time = distance ÷ speed, the time is 160 m ÷ 320 m/s = 0.50 seconds. The correct choice is 0.50 seconds.

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