Answer:
6.14 miles/hour
Explanation:
Charlie runs at a speed of 3 yards per second.
First we have to calculate the speed per hour in yards.
1 hour = 3600 seconds
In one second Charlie runs = 3 yards
in 3600 seconds he runs = 3600 × 3
= 10,800 yards
Since 1760 yards = 1 mile
Hence, 10,800 yards =

= 6.13636 ≈ 6.14 miles
Charlie runs at the speed of 6.14 miles per hour.