A 36-tooth gear turns three times. It is connected to a 12-tooth gear. How many times does the 12-tooth gear turn?
The gear ratio of meshed gears is in the inverse ratio of their teeth.
So the gear ratio of the 12-tooth gear to the 36-tooth gear is
To understand this, if the 12-tooth gear turns once, 12 teeth pass the point where the gears mesh.
Therefore 12 teeth on the 36-tooth gear also pass that point.
But 12 teeth on the 36-tooth gear is
So for every turn of the 12-tooth gear the large gear rotates
If the large gear turns 3 times the small gear turns