1. Ratios and Proportions
Intro to Algebra

2. RATIO
A comparison of two like quantities written in the form of a fraction a/b or a:b (a to b)

3. Ratios
The baseball game is 2/3 over. Your team is ahead 10 to 3. The proper fraction 2/3 and the score 10 to 3 are examples of ratios.

4. Think of some more real life ratios

5. Ratios about our Class

6. Ratios
In a class of 20 students, 11 are female and 9 are male. Write the following rations to describe the class.
Ratio of male to female students
Ratio of female to male students
Ratio of female students to the total
Ratio of male students to the total
Ratio of total number of students to females
Ratio of total number of students to males

7. Ratios
In a collection of 25 CDs, 17 are country music and 8 are classical music. Write the ratio of classical to country music in 3 different ways.

8. GCF
To express a ratio in simplest form, begin by writing the ratio as a fraction. Next, find the GCF of the numerator and the denominator. Divide both the numerator and denominator by the GCF.

9. Ratios
Express the ratios in simplest form:
15: 9
20 : 8

10. PROPORTION
A proportion is a statement made up of two equal ratios; a statement of the form

11. RULE FOR PROPORTIONS
In any proportion whenever a/b = c/d is true, then a·d = b·c is true. (cross multiply)

12. Example
Is 2/3 = 8/12 a true proportion?

13. Solve for x
3:x = 6:20