Hi dreelectron,

This is just a matter of knowing the formula for the circumference of the circle and doing a lot of unit conversions. I'll do the case where the wheel is traveling 5 mi/hr and let you do the others.

The circumference of the circle is

so the distance between two teeth is

.

The wheel is moving at a speed of

So the pulse rate is

[edit]I'm assuming the teeth are along the edge of the wheel. If that's not the case, you need to clarify your question.[/edit]