1. Proportions & Similar Figures
Less 4-1 Using Proportions

2. Proportions Review…
What is a ratio? The comparison of two numbers (given as a fraction) What is a proportion? When two ratios are equal to each other How do we solve for a proportion? Use cross products (cross x, cross x, ÷ to solve) How do we use proportions for solving for percentages? **(formula) “is #” = given/missing % “of #” 100%

3. Proportions & Similar figures
Similar figures = polygons of same shape, different size Missing sides of similar figures… …can be solved by proportions

4. Proportions & Similar figures
In the figure, ▲ABC is similar to ▲DEF. Find the missing length for side DE
AB = AC DF DE 15 = DE DE = 15 C E x 18
A B D F

5. Proportions & Similar figures
In the figure, ▲RST is similar to ▲XYZ. Find the missing length for side XZ S
R T Z 10
X Y
Find length XZ

6. Practice Find the length QR A 12 B C D Q R 3 S T 9
In the figure, ▀ ABCD is similar to ▀ QRST. Find the missing length for side QR
A B 9
C D
Q R 3
S T
Find the length QR