How do you calculate gear ratio using gear teeth counts Z1 and Z2, and how does it affect speed and torque?

• A. Gear ratio = Z2/Z1; speed_out = speed_in × Z1/Z2; torque_out = torque_in × Z2/Z1 × η.
• B. Gear ratio = Z1/Z2; speed_out = speed_in × Z2/Z1; torque_out = torque_in × Z1/Z2 × η.
• C. Gear ratio = Z2/Z1; speed_out = speed_in × Z2/Z1; torque_out = torque_in × Z1/Z2 × η.
• D. Gear ratio = Z1/Z2; speed_out = speed_in × Z1/Z2; torque_out = torque_in × Z2/Z1 × η.

Answer: (B)