If gear A has 20 teeth and meshes with gear B that has 60 teeth, when gear A makes 6 full rotations, how many rotations does gear B make?

Gear ratio = (teeth of driven gear) / (teeth of driver gear) = 60/20 = 3:1. When a smaller gear drives a larger gear, the larger gear rotates SLOWER but with more torque. Calculation: gear A (20 teeth, 6 rotations) — total teeth moved = 20 × 6 = 120 teeth. Gear B has 60 teeth, so 120 / 60 = 2 rotations. General principle: teeth pass at the same rate where gears mesh. Rotations of A × teeth of A = rotations of B × teeth of B. Gear systems: (1) SMALL driving LARGE: torque multiplied, speed reduced (used to lift heavy loads slowly); (2) LARGE driving SMALL: speed multiplied, torque reduced (used in bicycles for fast pedaling at high gear); (3) DIRECTION: meshing gears rotate in OPPOSITE directions; an idler gear between them keeps them rotating in the same direction; chain or belt drives between gears keep them rotating in the SAME direction. Gear trains: multiple gears in series — overall ratio is product of individual ratios. Bicycle gears: smaller front × larger back = easier pedaling (climbing); larger front × smaller back = faster speeds (flat ground). Common ASVAB MC questions: gear ratios, rotation counts, rotation direction, torque multiplication.