Question

find r.
write your answer as a whole number or a decimal. do not round.

Explanation:

Step1: Identify similar triangles

$\triangle ABC \sim \triangle DEC$ (AA similarity: right angles + vertical angles)

Step2: Set up proportion of sides

$\frac{r}{10} = \frac{4}{8}$

Step3: Solve for $r$

$r = 10 \times \frac{4}{8}$

Answer:

5