Chapter 3 Section 4
Ratio and Proportion!!!
1. What is a ratio? (pg 142):
2. There are many different ways to write ratios. Write the ratio of a to b in two other ways:
3. What is a rate? (Pg 142)
4. Main Street Florist sells two dozen roses for $24. 60. Flowers for You Florist sells six roses for $7.50. Which florist
has the lowest price per rose?
5. The answers you found in #4 is called a unit rate. What is the definition for a unit rate? (pg 142)
6. Write each of these ratios as a unit rate:
a.
$.72
16oz
b.
$1.20
32oz
c.
$1.60
64oz
7. In 2004, Lance Armstrong won the Tour de France, completing the 3391 km course in about 83.6 hours. Find
Lance’s unit rate, which is average speed. Cycling at his average speed, about how long would it take Lance to
cycle 185 km?
8. What is a proportion? (pg 144):
9. An example of a proportion is
2 8
 . Is this equation true? Does two thirds really equal 8 twelfths? Explain how
3 12
you would know.
10. You can use the numbers 2, 3, 8, and 12 to write these other true proportions:
2 8

3 12
3 12

2 8
a. Tell whether each proportion is a true proportion.
b. Explain how you could tell if they were true.
3 2

12 8
12 8

3 2
11. What do you think the missing value is in this proportion:
2 x
 ? How did you know?
3 6
12. Use what you know about solving equations to solve the proportion
2 x
 for x. (Show your work!)
3 6
13. Solve each of the following proportions with the method you used in #12.
a)
p 132

12 176
b)
21 q

35 20
c)
r
30

30 200
d)
130 n

78 5
STOP!! We will come together and do number 11 as a class!
14. Jennifer estimates that two out of every three students will attend the class party. She knows there are 750
students in her class. Set up and solve a proportion to help her estimate how many people will attend:
STEP 1: What are you trying to find out? Pick a variable to represent the information you’re trying to find: ______
STEP 2: Set up the proportion. Be sure that both ratios make the same comparison:
STEP 3: Solve the proportion for your variable.
15. Use the steps from #14 to solve the following problem on your own:
A box of cereal weighing 354 grams contains 20 grams of fat. Find the number of grams of fat in the
recommended serving size of 55 grams.
So far, in all of our proportions, the variable has been in the numerator. How could we solve a proportion with the
variable in the denominator??
16. Solve the following proportions with the variable in the denominator. (How could you use what you’ve already
done? Where does the variable need to be so that you’d know how to solve it? How do you get it there?)
a)
3 5

y 8
b)
5 10

g 6
c)
5 9

4 k
Use the following space to takes the rest of the notes on proportions:
17. Explain why you can use “cross products” as a short-cut to solving proportions
d)
15 4

x 3