Question

1. a photo measures 3 inches by 5 inches and needs to be enlarged to 9 inches by 15 inches. what is the scale factor?

a. 2
b. 4
c. 5
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. We can use either the length or the width to find the scale factor. Let's use the length. The original length is 3 inches and the new length is 9 inches.

Step2: Calculate the scale factor

The scale factor $k=\frac{\text{new length}}{\text{original length}}=\frac{9}{3}=3$. We can also check with the width. The original width is 5 inches and the new width is 15 inches. The scale factor $k = \frac{\text{new width}}{\text{original width}}=\frac{15}{5}=3$.

Answer:

d. 3