To find the scale factor used to create the printed photo of the sandbox, you can use the lengths of the sides of the original sandbox and the printed sides.
- Original side length: 40 inches
- Printed side length: 4 inches
The scale factor can be calculated by dividing the printed length by the original length:
\[ \text{Scale factor} = \frac{\text{Printed side length}}{\text{Original side length}} = \frac{4 \text{ inches}}{40 \text{ inches}} = \frac{1}{10} \]
So, the scale factor used to create the printed photo of the sandbox is \( \frac{1}{10} \).