PROPORTIONS AND GEOMETRY

In this lesson you will learn about• Similar and congruent figures• Corresponding sides and angles• How you can use ratios and proportions to determine

missing sides and angles in similar figures• What proportional equations might look like on a graph• How this information might apply to GED-type story

problems

“Similar Triangles”  (1966) Crocket Johnson

Crocket Johnson created over 100 paintings based on geometry.  Most of these are now in the Smithsonian.  Here is a link to the exhibit online  Smithsonian Exhibit

Vocabulary:

Congruent = same shape, same size

Similar = same shape, different size

Corresponding = matching

Practice

1. Name the similar triangles. 

A and B, C and D

2. Name the corresponding angles in triangles A and B.

2 and 4; 3 and 5

3. In the purple triangles , if side 6-8 is 6 inches and base 7-8 is 10 inches; and base 9-10 is 22 inches, what is the measure of side 6-10?

13.2

4. Are the any congruent triangles?

A

B D

C

4

1 6

87

9

2

10

5

3

Letters and numbers have been added for this exercise.

Mona Lisa The Mona Lisa is a

famous painting by Leonardo da Vinci.

It was painted around the year 1500.

It is about 20 x 30 inches.

It is currently in the Louvre museum in Paris.

Vocabulary:Congruent or Similar?

Congruent =

same shape and size

Similar = same shape

different size

Which two are similar? Congruent?

A B

C D

Mona Lisa Project:Your task is to size several reproductions of the Mona Lisa that are proportionally accurate to the original, which is approx 20 x 30 inches. In doing this you will discover more than one way to prove that something is proportional. See specific directions in your envelopes.

Some GED-type practice Practice graphing proportions