The Algebra Teacher\'s Guide to Reteaching Essential Concepts and Skills

Teaching Notes 1.6: Evaluating Expressions

Evaluating an expression requires students to replace each variable in an expression with a given

value and simplify the result. Common errors occur when students either substitute an incorrect

value for the variable or follow the order of operations incorrectly.

1. Review variables by explaining that a variable represents an unknown quantity. It is usually
   expressed as a letter.


2. Explain that sometimes students are required to find a variable’s value. At other times the
   value of a variable is provided. When the value of a variable is provided, students must
   replace the variable in the expression with that value.


3. Stress to your students the importance of substituting values for variables correctly.


4. Encourage them to rewrite the problem after they have substituted the correct values.


5. Review the order of operations and examples on the worksheet with your students. Cau-
   tion them to pay close attention to nested grouping symbols. Depending on their abili-
   ties, you may find it helpful to review 1.3: ‘‘Simplifying Expressions with Nested Grouping
   Symbols.’’

EXTRA HELP:

A number directly before a variable denotes multiplication. For example, 3ameans 3 timesa.

A number or variable above or below a fraction bar denotes division. For example,

a

4

means a

number divided by 4.

ANSWER KEY:

(1) 7 (2) 58 (3) 56 (4) 64 (5) 2 (6) 29 (7) 14 (8) 26

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(Challenge)Answers may vary. One acceptable response isc(d−a)−b.

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12 THE ALGEBRA TEACHER’S GUIDE