To solve this we need two conversion factors: 1yd = 3ft, and 1min = 60s. To convert the units, you need to manipulate the conversion factor so that the units in the denominator cancel the units in the denominator: (39ft/min) * (1yd/3ft) = 13yd/min. The units of ft cancel out leaving 13yd/min. (13yd/min) * (1min/60s) = 0.217yd/s
