In a gear train that uses an __ number of gears, the driven shaft rotation will be the same as the driver shaft rotation.

• A. Even
• B. Odd
• C. Prime
• D. Composite

Answer: (B)

Rotation direction in a gear train flips with every gear-to-gear contact. The driver’s rotation passes through each mesh, reversing at each step. The number of such reversals equals the number of gears minus one. If the train uses an odd number of gears, the number of reversals is even, so the driven shaft ends up rotating in the same direction as the driver. For example, with three gears, the first and last gears rotate the same way, while with four gears the last gear rotates in the opposite direction. Prime or composite labels don’t affect this; it’s about parity—an odd number of gears yields the same rotation direction.