Similar Figures

Similar Figures

Similar Figures

• same shape, different size

• think blowing up or shrinking an image on a copier

Multiple Choice

Which rectangle is similar to rectangle ABCD?

• Rectangle EFGH

• Rectangle PQRS

• Rectangle WXYZ

Multiple Choice

Which trapezoid is similar to trapezoid DEFG?

• Rectangle PQRS

• Rectangle WXYZ

• Rectangle JKLM

Multiple Choice

Which triangle is similar to triangle DEF?

• Triangle XZY

• Triangle ABC

• Triangle RST

Vocabulary

Corresponding Angles - angles in the same place on similar figures

Corresponding Sides - sides in the same place on similar figures

Scale Factor - ratio sides are multiplied by to find corresponding lengths on new or scaled figure

What do we know about similar figures?

•  $\angle A=\angle D$  
  

•  $\angle B=\angle E$  
  

•  $\angle C=\angle F$  
  

•  $\frac{15}{10}=\frac{9}{6}=\frac{12}{8}=\frac{3}{2}\ \left(Scale\ Factor\right)$  

•  $\Delta ABC\sim\Delta DEF$  

Multiple Choice

Write the scale factor for each pair of triangles. Remember to simplify.

• 2 : 5

• 5 : 2

• 14 : 35

• 16: 40

Find the Missing Side Length

• The triangles are similar so the ratios of corresponding sides are equivalent.

•  $\frac{6}{30}=\frac{5}{x}$  

•  $6x=150$  

•  $\frac{ }{6}\ \ \ \ \ \ \ \ \ \ \frac{ }{6}$  

•  $x=25$  

Find the Missing Side Length

•  $\frac{4}{9}=\frac{18}{x}$  

Open Ended

You are sitting around the dinner table and one of your grown ups asks what you learned in math today. What do you tell them? Remember to impress them by using the correct mathematical vocabulary!