Not sure exactly where to post this

I'm not sure if this would be more a geometry or algebra problem. I'm trying to figure out the process to find the answer to this problem.

I have a wheel that is 40 inches in diameter. On that wheel is a gear with 20 teeth. Each tooth actuates a magnetic sensor which in turn sends pulses to a controller. I'm trying to figure out how many pulses per second if the wheel is traveling 5, and 6, and 7 miles per hour and so on.

I'm sure there is an equation or string of equations that will give me the answer just not sure how to get there.

Please let me know if this needs to be in a different thread.

Thanks