A triangle has sides 4, 7, and 10.

Question

In a similar triangle the shortest side is 12 and the longest side is x.

Write a proportion that models the situation.

Solve the proportion for x.

Answer 1

If two triangles are similar, the ratio of shortest side to longest side will be the same.

The ratio of shortest side to longest side of the first triangle is 4/10.

The ratio of shortest side to longest side of the second triangle is 12/x.

4/10 = 12/x

If we cross multiply (multiply each side by both denominators), we get:

4x = 120

Dividing both sides by 4, we get the answer:

x = 30