Question

a photo measuring 2 inches by 3 inches needs to be enlarged to 6 inches by 9 inches. what is the scale factor?
a. 5
b. 2
c. 4
d. 3

Explanation:

Step1: Recall scale - factor formula

The scale factor is the ratio of the corresponding side lengths of the enlarged figure to the original figure.

Step2: Calculate scale factor using length

For the length, the original length is 2 inches and the new length is 6 inches. The scale factor $k=\frac{\text{new length}}{\text{original length}}=\frac{6}{2} = 3$.
We can also check with the width. The original width is 3 inches and the new width is 9 inches. The scale factor $k=\frac{\text{new width}}{\text{original width}}=\frac{9}{3}=3$.

Answer:

d. 3