To determine the scale factor used when drawing a bug that is 3 cm in reality but is represented as 10 cm in a picture, you can use the following formula:
\[
\text{Scale factor} = \frac{\text{Size in picture}}{\text{Actual size}} = \frac{10 \text{ cm}}{3 \text{ cm}}
\]
Calculating this gives:
\[ \text{Scale factor} = \frac{10}{3} \approx 3.33 \]
To express \( \frac{10}{3} \) as a mixed number:
- Divide 10 by 3, which gives 3 with a remainder of 1.
- So, \( \frac{10}{3} = 3 \frac{1}{3} \).
Thus, the scale factor used is \( 3 \frac{1}{3} \).