8.3A Similar Figures

Similar Figures and their Proportionality

Open Ended

What does it mean for two figures to be congruent?

• During translations, reflections, and rotations, the pre image and image are congruent

• During a dilation, the pre image and image are similar. Let's talk about the difference...

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Congruent vs Similar

Open Ended

What do you think is the difference between "congruent" and "similar."

Congruent figures are both the same size and the same shape. Therefore all the side lenghts of the image are the same as the pre image.

​​Congruent

​SImilar figures are the same shape but different sizes. What's special about them is their proportionality.

​​Similar

We can set up proportions of corresponding sides of similar figures to solve for a missing side length.

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Set up a proportion that could be used to find the length of side PQ.

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• Sometimes there are no numbers, just labeled vertices. But that's okay! We can still set up a proportion.

• Write 3 examples of proportions that would be true about the similar figures.

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​No Numbers?

Now You Try!

Multiple Choice

Which proportion would help to solve for x?

• $$\frac{\text{x}}{\text{13.2}}=\frac{\text{3}}{\text{6}}$$

• $$\frac{3}{x}=\frac{6}{13.2}$$

• $$\frac{3}{x}=\frac{6}{11}$$

• $$\frac{5}{3}=\frac{11}{x}$$

Multiple Choice

Which proportion is set up correctly?

• $$\frac{WX}{DC}=\frac{XY}{BC}$$

• $$\frac{AB}{WX}=\frac{BC}{ZY}$$

• $$\frac{AD}{WZ}=\frac{AB}{WX}$$

• $$\frac{XY}{BC}=\frac{WZ}{AB}$$

Thanks for listening!

Now you will try the practice problems assigned to you in Eduphoria. Do your best!