Gear Ratio Question

[ACEGUY]

A40-300 4000rpm@24V.

What is the end speed you want to reach with what size of wheels?

For example. A standard 6" solid polyurethane wheel and 25kph.
4000rpm*.152m*3.14=1914meters per minute
1914*60= 114840 meters per hour
114840mh/1000= 114,8Kph
114.8Kph/25Kph=4.5
Result = gearratio 1 to 4.5 15 tooth gear on the motor and a 68 tooth gear on the wheel.

what I'm looking at is a 10" pneumatic wheel with a top speed of 15mph, that's the hope anyway.