A motor drives a small gear with 10 teeth which is connected to a larger gear with 40 teeth. What is the gear ratio?

1. 4 : 1
2. 1 : 4
3. 1 : 2
4. 2 : 1

4 : 1

Reason — The driving gear is the gear that receives power directly from the motor and moves first. Here, the motor drives the small gear with 10 teeth, so it is the driving gear.

The driven gear is the gear that is moved by the driving gear. Here, the larger gear with 40 teeth is connected to the small gear and rotates because of it, so it is the driven gear.

The formula for gear ratio is:

$\text{Gear Ratio}=\dfrac{\text{Number of teeth on driven gear}}{\text{Number of teeth on driving gear}}$

Substituting the values:

$\text{Gear Ratio}=\dfrac{40}{10}=4$

Hence, the correct answer is 4 : 1.