S=d/t so in this case it's 75/12 which is 6.25. Round it and you got 6 miles per hour.
6.25 ;
The boy swims at a speed of approximately 6.25 feet per second. When converted to miles per hour, this is roughly 4.25 mph, rounded to 4 mph. Thus, his swimming rate is about 4 miles per hour.
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