Let's get Mathematical Part 6

Given: cannon pinion 12 leaves, minute wheel 40 teeth, minute wheel pinion 10 leaves. How many teeth does the hour wheel have? Ratio 12:1 Motion work (teeth:pinions):

N4 = Z1•Z3
N1 Z2•Z4

12 = 12x10
1 40x?

12 = 12x1
1 4x?

So 12x12 (ratio of teeth x number of pinion leaves) = 144
Divided by the known number of teeth (4) = 36

So the answer is 36. The hour wheel has 36 teeth.