Charlie runs at a speed of 3 yd./s about how many miles per hour does Charlie run

What is being asked here is to convert the value above from units of yards per second into miles per hour. To do this, we need a conversion factor to multiply to the value for it to be converted to another units. We do as follows:

Conversion Factors

1 mile = 1760 yards

1 hr = 3600 s

3 yd/s (1 mile / 1760 yards) (3600 s / 1 hr) = 10.8 miles per hour