Stretching & Shrinking
Summary 3.4
Finding Lengths with Similar Triangles
Vocabulary:
Nested Triangles-Overlapping triangles that share a common angle.
Example:
Find the value of x.
Step 1: Separate the triangles. Label each side length.
x
2.5 cm
7.5 cm
30 cm
Step 2: Determine the scale factor from one triangle to the other. (It is easier
to find the scale factor to the triangle with the missing side. In this case from
the small triangle to the large triangle)
30
30 ∙ 2 60
=
=
=4
7.5 7.5 ∙ 2 15
Step 3: Multiply 2.5 by the scale factor.
2.5 ∙ 4 = 10
Answer: x= 10 cm