Question

if these two shapes are similar, what is the measure of the missing length r?
12 km
52 km
18 km
r = \boxed{} kilometers
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Explanation:

Step1: Set up proportion for similar shapes

$\frac{12}{18} = \frac{52}{r}$

Step2: Simplify left ratio

$\frac{2}{3} = \frac{52}{r}$

Step3: Cross-multiply to solve for r

$2r = 52 \times 3$
$2r = 156$
$r = 78$

Answer:

78 kilometers