7.4 Class/Homework
What’s My Number?
Writing Algebraic Expressions
Sheldon Elementary School has a school store that is open every Thursday. It sells many items including
folders, pencils, erasers, and novelty items. The Parent Association at the school is in charge of buying the
items for the store.
1. One popular item at the store is scented pencils. The pencils come in packs of 24 from the retailer.
a.
How many pencils will they have available to sell if they buy 2 packs from the retailer?
b.
How many pencils will they have available to sell if they buy 6 packs from the retailer?
c.
How many pencils will they have available to sell if they buy 9 packs from the retailer?
d.
Write a sentence to describe how you can determine the amount of pencils available to sell for any
number of packs purchased.
e.
Write an algebraic expression that represents the total number of pencils they will have available to
sell. Let p represent the number of packs of pencils they purchase from the retailer.
2. The latest fad is animal-shaped rubber bracelets. Because of their popularity, the Parent Association wants to
buy packs of them in bulk. They decide to shop around to find the best price.
a.
Store A sells 24 packs for $47.76. What is the cost per pack?
b.
Store B sells 24 packs for $48.00. What is the cost per pack?
c.
Store C sells 24 packs for $46.80. What is the cost per pack?
d.
Write an algebraic expression that represents the cost per pack of bracelets. Let c represent the cost of
24 packs.
e.
Write the meaning of the algebraic expression from part (d). Then, evaluate the expression for c =
49.20. Explain your answer in terms of the cost per pack of bracelets.
3. The store decides to have a clearance sale the last week of school. The expression 14  n represents the
number of folders they have at the end of the sale.
a.
Write the meaning of the algebraic expression in two ways. Then, explain what the expression means
in terms of the number of folders.
b.
Complete the table to represent the numbers of folders they could have left at the end of the sale.
n
2
5
14  n
11
13
14
What’s My Number?
Writing Algebraic Expressions
Vocabulary
Write the term from the box that best completes each statement.
evaluate an algebraic expression
constant
numerical coefficient
4. To ______________________________ means to determine the value of the expression.
5. A number, or quantity, that does not change its value is called a(n) ___________________.
Problem Set
Calculate the answers for each situation. Then, write a sentence to explain how you can determine the answer
for any amount given.
6. The PTA sells school-spirit pencils to raise money for the school. Each pencil costs 35¢. How much money is
raised if they sell 200 pencils? 550 pencils? 1200 pencils?
Write an algebraic expression that represents each situation.
7. You can type 90 words per minute. How many words can you type in m minutes?
8. You have 4 key chains on your backpack. How many key chains will you have if you get k more key chains
over the summer?
9. You buy 100 yo-yos to give away as prizes at a carnival. If p people win a prize, how many yo-yos will you
have left?
10. You want to store an equal number of books on each of the 5 shelves on your bookcase. If you have b books,
how many books will be on each shelf?
11. Bulk trail mix costs $1.95 per pound. How much will you pay for t pounds of trail mix?
Write an algebraic expression that represents each word expression.
12. thirty-four more than a number, h
13. sixteen minus m
14. twenty-eight divided by s
Write the meaning of each algebraic expression. Then, evaluate the algebraic expression for the given value.
15. 6a + 11 if a = 8
16. 7x  9 if x = 3
17. 34  y2 if y = 5
Complete each table. Identify the relationship between the two columns given by the algebraic expression.
18.
c
2c  8
4
9
8.5
19.
z
1
3
7
2.2
20.
k
0
5
2.5
7
9 + 2z
7.4 Class/Homework
Answer Section
1. ANS:
a.
24(2) = 48
They will have 48 pencils to sell if they buy 2 packs.
b.
24(6) = 144
They will have 144 pencils to sell if they buy 6 packs.
c.
24(9) = 216
They will have 216 pencils to sell if they buy 9 packs.
d.
I could multiply the number of packs of pencils purchased by 24 to determine the number of pencils
they will have available to sell.
e.
24p
PTS: 1
TOP: Assignment
2. ANS:
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
KEY: numerical coefficient | constant | evaluate an algebraic expression
a.
The cost per pack is $1.99.
b.
The cost per pack is $2.00.
c.
The cost per pack is $1.95.
d.
e.
c divided by 24
The cost per pack is $2.05.
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Assignment KEY: numerical coefficient | constant | evaluate an algebraic expression
3. ANS:
a.
Fourteen minus n or n less than 14
The store has 14 folders to sell. The letter n represents the number of folders they will sell at the
clearance sale. So, 14  n represents the number they will have left at the end of the sale.
b.
n
14  n
2
12
5
9
11
3
13
1
14
0
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Assignment KEY: numerical coefficient | constant | evaluate an algebraic expression
4. ANS: evaluate an algebraic expression
PTS:
TOP:
KEY:
5. ANS:
1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
Skills Practice
numerical coefficient | constant | evaluate an algebraic expression
constant
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
6. ANS:
0.35(200) = 70
When 200 pencils are sold, $70 is raised.
0.35(550) = 192.50
When 550 pencils are sold, $192.50 is raised.
0.35(1200) = 420
When 1200 pencils are sold, $420 is raised.
I can multiply the number of pencils sold by 35¢ (0.35) to determine the amount of money raised.
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
7. ANS:
90m
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
8. ANS:
4+k
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
9. ANS:
100  p
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
10. ANS:
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
11. ANS:
1.95t
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
12. ANS:
h + 34
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
13. ANS:
16  m
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
14. ANS:
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
15. ANS:
6 times a plus 11
6(8) + 11  First multiply 6 by 8. Then, add 11.
48 + 11
59
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
16. ANS:
7 times x minus 9
7(3)  9  First multiply 7 by 3. Then, subtract 9.
21  9
12
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
17. ANS:
34 minus y squared
34  52  First find 52. Then, subtract the result from 34.
34  25
9
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
18. ANS:
c
2c  8
4
0
9
10
1
8.5
9
Each value in the right column is 8 less than 2 times the corresponding value in the left column.
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
19. ANS:
z
9 + 2z
1
11
3
15
7
23
2.2
13.4
Each value in the right column is 9 plus two times the corresponding value in the left column.
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression
20. ANS:
k
0
4
5
6
2.5
5
7
Each value in the right column is 4 more than 2 times the corresponding value in the left column, divided by
5.
PTS: 1
REF: 7.4
NAT: 6.EE.2.a | 6.EE.2.b | 6.EE.2.c | 6.EE.6
TOP: Skills Practice
KEY: numerical coefficient | constant | evaluate an algebraic expression