1. RATIOS & PROPORTIONS
By: Ms. D. Kritikos

2. A ratio is a comparison of the numbers of two sets.
Ratio of ‘s to ‘s.
3 to 5
Ratio of ‘s to ‘s.
5 to 3

3. In the following problems, express the ratio of the number of the first set to the number of the second set in two ways: as a ratio and as a fraction.

4. PRACTICE PROBLEMS: SET #1 SET #2 1. ( , ) (*, , ) 2 to 3
1. ( , ) (*, , )
2 to 3
2. (Jim, John) (Jo, Sue, Ann, Kay)
2 to 4 OR 1 to 2
Ratios can be reduced just like fractions.

5. PRACTICE PROBLEMS: SET #1 SET #2 3. (1, 2, 3, 4) (a, b, c) 4 to 3
4. (Bob, Dick, Al) (1st, 2nd, 3rd)
3 to 3 OR 1 to 1

6. PRACTICE PROBLEMS: (Express each as a ratio and a fraction)
5. 7 runs in 9 innings
7 to 9
6. 3 teachers for 72 students
3 to 72 OR 1 to 24
7. 6 goals for 9 shots
6 to 9 OR 2 to 3

7. A proportion expresses the equality of two rates.
is a proportion because
is true.
12 is equal to 12
Remember to cross multiply.
is not a proportion because
is false.
20 is not equal to 24

8. Practice Problems: (State if a proportion and explain why or why not.)
Is not a proportion because
is false.
32 does not equal 35
is a proportion because
is true.
36 equals 36

9. How to solve proportions
EXAMPLE#1:
EXAMPLE#2:
Cross multiply
5n=120
48=3n
n=24
16=n

10. Practice Problems: Problem#1: Problem#2: 120=6n 24n=120 20=n n=5
Cross multiply
120=6n
24n=120
20=n
n=5

11. to practice on the worksheet.
It’s your turn now…
to practice on the worksheet.