The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the **number of teeth** each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear. For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.

If you have a gear train with two gears, the first with 36 teeth and the second with 8 teeth, how many revolutions does the second gear make for each revolution of the first gear?

4.5 | |

2.3 | |

7.5 | |

4.1 |