The number of teeth on driven gear is 30 and on driving gear is 15. Find the gear ratio.

Given:

Number of teeth on driven gear = 30

Number of teeth on driving gear = 15

The formula for gear ratio is:

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

Substituting the values:

$\text{Gear Ratio}=\frac{30}{15}=\frac{2}{1}$

Hence, the gear ratio is 2 : 1.