Question

Find the unknown length given that the triangles are similar

Answer 1

Use a proportion.

9/15 = 12/x

Cross multiply.

9x = 15 * 12

9x = 180

x = 20

Answer: 20 mm

Answer 2

Hello!

On one side, the length is 6 mm on the small triangle, and on the big one, it's 10. The ratio is 6:10

You can make a proportion

$\frac{6}{10} = \frac{12}{x}$

Cross multiply

10 × 12 = 120

Divide by 6 to get x

120 ÷ 6 = 20

$\framebox{x = 20 mm}$