Name ________________________________________ Date __________________ Class__________________
Proportional Relationships
LESSON
X
3
Review for Mastery: Solving Proportions
Solving a proportion is like solving an equation involving fractions.
• Multiply both sides of the equation by the denominator of the fraction
containing the variable.
• If the variable is in the denominator, invert both fractions in the
proportion.
20
28
n
7
20
7•
28
n
7•
7
n
7 • 20
28
n
5
140
28
12
x
9
6
x
12
6
9
12 •
x
12
x
12 • 6
9
x
8
Invert both
fractions.
12 •
6
9
72
9
1.
____
•
a
2
27
18
a
2
27
• ____
18
a
27 •
18
a
a
2.
____
•
8
12
n
9
8
12
n
• ____
9
•8
12
18
12
n
____
n
3.
____
•
10
t
4
6
t
10
6
4
t
10
n
t
____
t
t
4.
x
15
8
10
________________________
5.
7
3
w
18
6.
_______________________
4-24
3
2
6
• ____
4
6•
4
4
____
15
c
________________________
Holt McDougal Mathematics
© Houghton Mifflin Harcourt Publishing Company
Solve the proportion.
Name ________________________________________ Date __________________ Class__________________
LESSON
X
3
Proportional Relationships
Review for Mastery: Solving Proportions (continued)
You can use proportions to solve word problems.
A fruit punch is made with 32 ounces of ginger ale for every
12 ounces of frozen orange juice concentrate. How much ginger ale
should you use for 30 ounces of orange juice concentrate?
• Set up a proportion comparing the amounts
of ginger ale to orange juice concentrate.
• The first ratio shows the given recipe for
the fruit punch.
1st ratio 2nd ratio
ginger ale
orange juice concentrate
• The second ratio shows the unknown
amount of ginger ale as the variable g.
32
12
g
30
• Then solve the proportion.
32
12
g
30 •
30
g
30
30 •
30 • 32
12
80
g
g
32
12
960
12
© Houghton Mifflin Harcourt Publishing Company
You should use 80 ounces of ginger ale for 30 ounces of frozen
orange juice concentrate.
Solve.
7. Pecans cost $8.25 for 3 pounds.
What is the cost of 5 pounds of
pecans?
dollars
pounds
c
___________
8. Mandy drove 90 miles in 2 hours at a
constant speed. How long would it
take her to drive 225 miles at the
same speed?
c
miles
hours
____________________
h
___________
h
____________________
9. Last week Geraldo bought 7 pounds
of apples for $5.95. This week apples
are the same price, and he buys 4
pounds. How much will he pay?
10. Aretha can type 55 words per minute.
At that rate, how long will it take her
to type a letter containing 935
words?
________________________________________
________________________________________
4-25
Holt McDougal Mathematics
15. n
15
16. m
17. c
6
18. s
40
19. e
8.8
20. v
4.25
21. a 11.2
23. 7 eggs
45
Challenge
Do quantities
increase or
decrease? Proportion
22. $7.50
1. both increase 40 gal; 10 d 50 gallons
2. both decrease 80 lb; 2 yd 8 pounds
3. both increase 2.5 c; x c 3.75 cups
6
1in
5 inches
4. both increase
60 mi
Practice C
1. x
21
2. z
20
3. a
36
4. r
65
5. f
82
6. k
66
8. t
35
10. h
51
7. w
9. j
21
85
11. d
11.9
12. c
133
13. m
6.3
14. e
104
15. s
25.9
16. Possible answer: 40
50
64
80
17. Possible answer: 7
56
9
72
50
18. Possible answer: 15
45 150
19. 675 pounds
20. 66 pounds
5. both increase
© Houghton Mifflin Harcourt Publishing Company
1. 2; 2
2;
54;
3
2. 9; 9
9
72
6
3. 10; 10
10;
60;
15
4. x
12
5. w
6. c
10
7. 8.25 ; 5; $13.75
3
4 ;x
$1.50
$3.75
Problem Solving
1.
3.
4.
5.
7.
9.6, or $9.60
2. 80 grams
16 inches
1,015 pounds of honey
C
6. J
B
8. H
Reading Strategies
1. yes
2. no
3. yes
4. no
5. If the cross products of two ratios are
equal, the ratios form a proportion.
Review for Mastery
42
Answer
Puzzles, Twisters & Teasers
1. A
3. L
5. H
7. F
9. N
11. L
13. F
ALL THE FANS
2. L
4. T
6. E
8. A
10. S
12. E
14. T
LEFT
8. 90 ; 225; 5 hours
2
9. $3.40
10. 17 minutes
A33
Holt McDougal Mathematics