1. Ratio A ratio is a comparison of two numbers such as a : b. Ratio:
When writing a ratio, always express it in simplest form.
Example: A B C 6 8 10
Now try to reduce the fraction.
Type notes here

2. Proportion
Proportion: An equation that states that two ratios are equal.
Terms
First Term
Third Term
Second Term
Fourth Term
Type notes here
To solve a proportion, cross multiply the proportion

3. Practice Reduce the following fractions. 1) 2) 3)
1) 2) 3)
Solve the following equations. What is the method?
4) 5) 6)

4. Practice worksheet On my website www.mshalllovesmath.wordpress.com
Period 2
Proportions

5. Standard
G-SRT 2 Given two figures, use the definition of similarity in terms of similarity transformations to decide if they are similar; explain using similarity transformations the meaning of similarity for triangles as the equality of all corresponding pairs of angles and the proportionality of all corresponding pairs of sides.

6. Objective
Using prior knowledge of proportions and angles and given knowledge about similar triangles students will determine if triangles are similar.

7. Similar Figures Definition: Two figures are similar if
their corresponding sides are proportional, and
their corresponding angles are equal.
Similar figures have the same shape but possibly different sizes.
Similarity
Statement:
ΔABC ~ ΔDEF
Notes:
~ => “is similar to”
The order of the letters matters! A D E B F C

8. Match pairs of similar shapes.

9. The fractions all reduce to a common similarity ratio.
1) Corresponding angles are congruent:
2) Corresponding sides are proportional: A D F E C B = =
The fractions all reduce to a common similarity ratio.

10. N  Q and P  R, M  T Example 1
Identify the pairs of congruent angles and corresponding sides.
0.5
N  Q and P  R, M  T

11. Example 2
Identify the pairs of congruent angles and corresponding sides.
B  G and C  H, A  J.

12. Ex 3. Identify the pairs of congruent angles and corresponding sides.
85° 14 2
85°
45°
50°
45°
50°
Are the triangles similar? How do you know?

13. Identify the pairs of congruent angles and corresponding sides.
N  M, L  P, S  J

14. Identify the pairs of congruent angles and corresponding sides.
85°
85°
45°
50°
45°
50°
Identify the pairs of congruent angles and corresponding sides.

15. Polygon
Determine whether the polygons are similar. If so, write the similarity ratio and a similarity statement.
A  E, B  F,
C  G, and
D  H.

16. Ratios and Proportion worksheets and similar figures and proportions
Picture frame problem

17. Objective: Students will use their prior
knowledge on proportions, and similarity
to solve for a missing side.

18. Example 1 ∆SUT ~ ∆SRQ. Use a proportion to solve for x.7 R S 18 21 x Q U T

19. Set up a proportion and find x.
Example 2:
Set up a proportion and find x.
ΔRDE ~ ΔAML 12 M L A 9 R x 8 E D

20. Example 3
∆SUT ~ ∆SRQ. Use a proportion to solve for x. x 3 3 5 x

21. Example 4
∆PST~ ∆PQR
Solve for x. x 4 12 6

22. More practice with proportions and similar figures
Go to
Click on your period and open the link
More practice with proportions and similar figures
Work on it on paper or on adobe reader

23. G.SRT.3 Use the properties of similarity transformations to establish the AA criterion for two triangles to be similar.
Objective: Students will investigate AA criterion and SSS criterion for triangle similarity and be able to use the criterion to identify similar triangles

24. Side-Side-Side (SSS~)M Q a c d f P b R L N e
If ___ = ___ = ___, then the triangles are similar.
Note: If sides are proportional, then corresponding angles must be congruent, and the Δs ~.

25. Example 1: Are the two triangles similar. Why or why not
Example 1: Are the two triangles similar? Why or why not? What is the similarity statement? Δ_______ ~ Δ ________ If m∠T = 39° and m∠R = 57°, find the measures of the remaining angles in both triangles.
Are they giving us side lengths or angle measures? W Z 12 9 3 4 H T 6 R K 8
Missing Angle Measure- 84

26. Example 2: Are the two triangles similar. Why or why not
Example 2: Are the two triangles similar? Why or why not? What is the similarity statement? Δ_______ ~ Δ ________ If m∠T = 41° and m∠R = 67°, find the measures of the remaining angles in both triangles.
Are they giving us side lengths or angle measures? W Z 9 5 18 10 H T 8 R K 16
Missing Angle Measure- 84

27. Angle-Angle (AA ~) M Q a c d f b R P L N e
If _____ pairs of ________________ angles are ______________, then the triangles are similar. 2
corresponding
congruent
Note: If ∠____ ≅ ∠ ____ and ∠ ____≅ ∠____, then the corresponding sides must be proportional and the Δ’s ~..

28. Are they giving us side lengths or angle measures?
Example Are the two triangles similar? Why or why not? What is the similarity statement? Δ_______ ~ Δ ________ B
53° C S 12
61 °
53°
61° F E Q 66

29. Focus Question
Why do we only need to show that TWO pairs of corresponding angles are congruent to prove similarity? Think: How did you find the missing angle in BOTH triangles?
61 ° B
53° F C E Q S
61°

30. Example: Are the two triangles similar? Why or why not?
35°
58°
32 and 55
NO not similar

31. Classwork #3
See Worksheet “CW #3 SSS~ and AA~”