AGENDA 4/16/12

• 1. Discuss Fractions “Quiz” with your table• 2. Intro to Ratio and Proportion• 3. Setting Up Ratios• 4. Proportion• 5. Proportion Word Problems

RATIO A ratio is a comparison of numbers by

division.

A ratio can be written with the word to, with a colon (:), or as a fraction.

Should always be reduced (simplifying)

Three Ways to Write a Ratio

3 to 2 3:2

RATIO TIPSThe numbers in a ratio MUST be written

in the order the problem asks for.

Always reduce a ratio to lowest terms.

When a ratio is an improper fraction, DO NOT change it to a mixed number.

Setting Up Ratios: Steps

1. Read the problem carefully.

2. Pay attention to the order the question wants you to write the ratio.

3. Set up the ratio appropriately.

4. REDUCE!!!!!

RATIO Evelyn earns $2400 a month. She pays $600 a

month in rent. What is the ratio of her income to her rent.

Make a ratio with her income first (in the numerator) and her rent second.

incomerent

2400600

246

41

For every $4 she makes,

She spends $1 on rent

RATIO In a factory, there are 150 men and 100

women working.

To compare these facts, write a ratio of men to women working in the factory.

menwomen

150100

1510

3 men2 women

Practice 1-6 pg 138

1. 24:30 =

200:125 =

28 = 21

Practice 1-6 pg 138

2. 3.4 = 1.7

4 to 1000 =

$560 to $320

Practice 1-6 pg 138

3. Alvaro makes $600 a week and saves $60 a week. What is the ratio of the amount he makes to the amount he saves?

Practice 1-6 pg 1384. For Alvaro, in problem 3,

what is the ratio of the amount he saves to the amount he makes?

Practice 1-6 pg 138 5. There are 24 students in Sam’s English

class. Four of the students speak Armenian as a first language. What is the ratio of Armenian speakers to the total number of students in the class?

PRACTICE 1-6 PG 138

6. Anna drove 110 miles on 22 gallons of gas. What is the ratio of the distance she drove to the number of gallons of gas she used?

TWO-STEP RATIO PROBLEMS

When you are not given both numbers you need, you may have to determine one of the numbers.

TWO-STEP RATIO PROBLEMS On a test with 20 problems, Maceo got 2

problems wrong. What was the ratio of the number of problems he got right to the total number of problems?

Step 1: Find the number of problems he got right.

Step 2: Make a ratio of the number of problems he got right to the total number of problems.

Reduce.

20-2= 18problems right.

righttotal

1820

910

EXERCISE 2, PAGE 139

1. A GED class of 20 students has 12 women. A.) What is the ratio of the number of

women to the total number of students? B.) What is the ratio of the number of men

to the total number of students? C.) What is the ratio of the number of men

to the number of women? D.) What is the ratio of the number of

women to the number of men?

EXERCISE 2, PAGE 139

2. At Baxter Electronics there are 105 union workers and 45 nonunion workers.

A.) What is the ratio of the number of union workers to the total number of workers?

B.) What is the ratio of the number of nonunion workers to the total number of workers?

C.) What is the ratio of the number union workers to the number of nonunion workers?

D.) What is the ratio to the number of workers to the number of union workers?

EXERCISE 2, PAGE 139

From a total yearly budget of $18,000,000, the city of McHenry spends $3,000,000 on education. What is the ratio of the amount spent on education to the amount not spent on education?

EXERCISE 2, PAGE 139

4. A math test of 50 questions included 15 fraction problems and 5 decimal problems. What is the ratio of the total number of fraction and decimal problems to the number of questions on the test?

EXERCISE 2, PAGE 139

5. There are 1213 registered voters in Paul’s village. During the last election 887 people actually voted. Which of the following is approximately the ratio of the number of people who voted to the total number of registered voters?

PROPORTION• A statement that says two ratios (or two

fractions) are equal.

2:4 = 1:2Proportion Statements

PROPORTIONS• Remember: cross products of equal fractions

are equal

44 =

• Each of the four numbers in a proportion is called an ELEMENT or a TERM.

• A letter usually represents the missing term.

PROPORTIONS

HOW TO SOLVE• Step 1: Write a statement with two equal

cross products.• Step 2: Divide both sides of the statement by

the number in front of the missing term.

=

• Solve for c in

• Step 1: Write a statement with two equal cross products.

• Step 2: Divide both sides of the statement by the number in front of the missing term.

HOW TO SOLVE

• Solve for y in the proportion 5:y=2:8

HOW TO SOLVE

• Step 1: Write a statement with two equal cross products.

• Step 2: Divide both sides of the statement by the number in front of the missing term.

If 12 yards of lumber cost $40, how much do 30 yards of lumber cost?

•

Step 1: Set up two ratios of yards to cost.

Step 2: Find both cross products.

Step 3: Divide both sides of the proportion.

Carlos got 2 problems wrong for every 5 problems right on a test. How many problems did Carlos get wrong if there were 35 problems on the test?

•

• Step 1: Set up two ratios of wrong to total

• Step 2: Find both cross products.

• Step 3: Divide both sides of the proportion.

The ratio of the number of men to the number of women working in the county hospital is 2:3. If 480 women work in the hospital, how many men work there?

•

• Step 1: Set up two ratios of ________to ________.

• Step 2: Find both cross products.

• Step 3: Divide both sides of the proportion.

Manny Drove 110 miles in 2 hours. Which expression shows the distance he can travel in 5 hours if he drives at the same speed?

•

• Step 1: Set up two ratios of ________to ________.

• Step 2: Find both cross products.

• Step 3: Divide both sides of the proportion.