Gear Ratio Math for Cim Motor FP801-005

[KogaVanDragon]

Please post if this math is correct and if it isn't please post what is incorrect. Any and all help is appreciated.

First Robotics Cim Motor (FP801-005) Gear Ratio
Formulas:
C = 2 x 3.1415 x R
In/min = RPM x C
MPH = In/min x (1 ft / 12 in) x (1 mi / 5280 ft) x (60 min / hr)
The Gear Ratio = MPH / New MPH
The Gear Ratio = Driven Gear / Driving Gear
Given:
Total Amps = 120 amps (Can't go over)
Cim Motor FP801-005= 40 amps (Amount Mr. Clark gave us to use)
RPM of Cim Motor FP801-005 = 1600 RPM (Looking under 40 amps)
Diameter of Wheel = 8 in
Radius of Wheel = 4 in
Goal MPH = 7 mph
Circumference:
C = 2 x 3.1415 x R
C = 2 x 3.1415 x 4 in
C = 25.1327 in
Curent In/min:
In/min = RPM x C
In/min = 1600 RPM x 25.1327 in
In/min = 40212.32 in/min
Current MPH:
MPH = In/min x (1 ft / 12 in) x (1 mi / 5280 ft) x (60 min / hr)
MPH = 40212.32 in/min x (1 ft / 12 in) x (1 mi / 5280 ft) x (60 min / hr)
MPH = 38.07984848 mph ( The goal was 7 mph so we need a gear ratio)
Gear Ratio:
Gear Ratio = MPH / New MPH
Gear Ratio = 38.07984848 mph / 7 mph
Gear Ratio = 5.439978354 (This can round down to 5 if that is easier because its mph will be 7.6 (in our goal range))