Question

scale factor:

Explanation:

Step1: Identify corresponding side lengths

Let's consider the horizontal side of the smaller triangle from $R(1,2)$ to $V(5,2)$ with length $5 - 1=4$. The corresponding horizontal side of the larger triangle from $R'(5,8)$ to $V'(21,8)$ with length $21 - 5 = 16$.

Step2: Calculate scale - factor

The scale factor $k$ is found by dividing the length of the side of the larger figure by the length of the corresponding side of the smaller figure. So $k=\frac{16}{4}=4$.

Answer:

4