answer:As long as all the gears will mesh, it’s just a matter of counting teeth. For a simple example, if one gear has 10 teeth and a second has 20, then you have a 2/1 or ½ gear ratio depending on which gear is the drive gear and which is driven. Let’s say the 10-tooth gear is hooked up to a motor turning at 100 RPM. For each complete revolution it makes, it will advance 10 teeth on the driven or output gear, so it will take 2 revolutions of the drive gear to yield one revolution of the output gear. You’ll have an output shaft turning at 50 RPM, but since the total amount of energy is conserved, halving the speed doubles the torque (with minor losses for friction, of course). If you reversed the situation and had the 20-tooth gear on the shaft of a 100 RPM motor, the 10-tooth gear would make 2 complete revolutions for each 1 the motor makes, so it would step up the speed to 200 PRM. But again, since total energy is calculated from speed and force, the torque of the motor would be cut in half. This math carries on as you add more gears, so you could easily build a clock that rotates its minute hand 1 time in 60 minutes with a drive motor running accurately at 6,000 RPM and a set of gears that reduces that speed by a factor of 6000/1.