Question

a drawing that measures 7 inches by 10 inches needs to be enlarged to 21 inches by 30 inches. what is the scale factor?
a. 2
b. 3
c. 2.5
d. 3.5

Explanation:

Step1: Recall scale - factor formula

The scale factor $k$ is found by dividing the new length by the original length. We can use either the length or the width of the drawing. Let's use the length. The original length $l_1 = 7$ inches and the new length $l_2=21$ inches.
The formula for the scale factor is $k=\frac{l_2}{l_1}$.

Step2: Calculate the scale factor

Substitute $l_1 = 7$ and $l_2 = 21$ into the formula: $k=\frac{21}{7}=3$.

Answer:

B. 3