Download Use Variables to Write Algebraic Expressions

EE
SKILL 32
Use Variables to Write
Algebraic Expressions
TEACHING STRATEGY
ALTERNATE INTERVENTION STRATEGY
1. Vocabulary Make sure students understand
the terms variable and expression. If students
confuse the terms expression and equation,
ask a volunteer to explain the difference.
Students should understand that an expression
does not contain an equal sign, while an
equation does.
Materials: index cards
2. Teach Point out to students that an algebraic
expression is a mathematical way of writing
a word phrase. Explain that associating key
words with the correct operation is critical to
being able to make the connection between
words and algebra. Provide students with
examples of simple phrases and real-life
situations. Ask What operation is described in
the phrase the product of x and 18? Explain.
[Answer: Multiplication; the key word product
indicates multiplication is used and x and 18
are the factors in the expression.] Ask If you
are x years old and your sister is 5 years older,
what expression could you write to show your
sister’s age? [Answer: x 1 5]
• Have one student hold up an index card.
• Have each student in the group read aloud
the expression.
• Try to get students to use as many different
phrases as possible. For example, “6 1 4”
can be read as 6 plus 4, the sum of 6 and 4,
4 added to 6, and so on.
• Ask students to record each phrase on an
index card.
3. For each expression, have students replace
one of the numbers with a variable. For
example:
a 1 4, 7 2 b, 4 · t, and m 4 9.
3. Quick Check Look for this common error as
students solve the Quick Check exercises.
• Using the wrong operation in an expression
as a result of misunderstanding key words
and the operations associated with them.
Strategy: Use index cards to write algebraic
expressions for a word expression.
1. Write on each index card a numeric expression
such as: 6 1 4, 7 2 3, 4 · 2, and 18 4 9.
2. Divide students into groups of four.
4. Again, have students in each group read the
expression aloud using different phrases.
Record each phrase on an index card.
5. Remove the algebraic expressions. Distribute
the index cards with the algebraic expressions
in word form and have students write the
algebraic form.
4. Next Steps Assign the practice exercises
to students who show understanding. For
students who need more support, provide
tutoring using the alternate teaching strategy.
Additional Teaching Resource
Online Transition Guide with Reteach
and Extra Practice worksheets from
previous grade levels
Transition Guide Course 1
(M)MIF6_TranG_NS31_34.indd 83
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EE
SKILL 32
Name
Date
Use Variables to Write
Algebraic Expressions
Example 1
Example 2
Write an algebraic expression for the following.
Write an algebraic expression for the following.
The product of p and 30
The sum of 28 and x
The word product indicates multiplication. So p
and 30 are factors in the expression: p · 30.
The word sum indicates addition. So 28 and x are
addends in the expression.
A product of a number and a variable can be
rewritten as a single term. The number is written
before the variable.
28 1 x
30p
Quick Check
Write an algebraic expression for each of the following.
1 Divide 16 by y.
2 The product of s and 13
3 Subtract 5 from t. Practice on Your Own
Write an algebraic expression for each of the following.
5 Subtract y from 7. 7 The product of d and 56 84
6 The sum of 10 and x
8 Divide m by 9.
© Marshall Cavendish International (Singapore) Private Limited.
4 The sum of 34 and c
Math in Focus: Singapore Math
(M)MIF6_TranG_NS31_34.indd 84
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Practice on Your Own
5.
6.
7.
8.
Practice on Your Own
y
4210
difference
sum
product
quotient; divisor, dividend
B
10
D
9
8
Skill 31
Quick Check
1. >
3. >
6
2. <
4. 5
E
4
3
6.
8.
10.
12
<
5
<
>
>
C
5
Practice on Your Own
5.
7.
9.
11.
13.
G
7
A
2
>
>
<
5
F
1
0
1 2
3
4 5
6
7 8
x
9 10
Skill 35
Skill 32
Quick Check
Quick Check
16
1. y
2. 13s
3. t 2 5
4. 34 1 c
Practice on Your Own
5. 7 2 y
6. 10 1 x
7. 56d
m
8.
9
1. (2, 4)
3. (3, 0)
2. (0, 6)
4. (1, 5)
Practice on Your Own
5. (5, 1)
7. and 8.
6. (0, 4)
y
10
9
Skill 33
8
Quick Check
1. 17 and 23
3. 14 and 2
2. 9 and 6
4. 0 and 4
6
K
5
4
Practice on Your Own
5. 22 and 8
7. 32 and 12
7
6. 18 and 66
8. 7 and 35
3
2
J
1
Skill 34
0
1 2
3
L
4 5
6
7 8
9 10
x
Quick Check
y
123
Skill 36
Quick Check
5
A
3
2
1 2
3
2. 28, 24, 21
Practice on Your Own
C
1
0
1. 25, 23, 22
3. 210, 27, 25
B
4
4 5
x
4. 211, 26, 23
6. 210, 29, 2
5. 213, 211, 22
Transition Guide Course 1
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8/15/11 9:15 AM