Education Technology

# Expressions and Equations / What is a Variable?

Grade Level 6,7
Activity 2 of 18
In this lesson students evaluate expressions, write expressions that correspond to given situations, and use expressions and formulas to solve problems.

## Planning and Resources

Objectives
Students should understand that a variable can take on any one of a range of values.  They recognize an algebraic expression as one involving some combination of variables, numbers and mathematical operations.

Vocabulary
expression
variable
constant

Standard:

## Lesson Snapshot

#### Understanding

Algebraic expressions specify numerical calculations using numbers and letters or symbols standing for numbers.

### What to look for

Students leave behind the symbol “x” for multiplication and come to understand that the juxtaposition of a number and a variable such as 3x implies multiplication between 3 and x.

### Sample Assessment

If a=115 and b=45, what would be the value of the expression b+(a - b)?

a 115  b. 185  c. 205  d. 275

Answer: a. 115

#### The Big Idea

A variable might stand for a range of numbers that can be used in a mathematical expression; a variable might be used in a universal statement that is true for all numbers; or a variable might stand for a specific value such as the solution to an equation or word problem.

### What are the students doing?

Students evaluate expressions, write expressions that correspond to given situations, and use expressions and formulas to solve problems.

### What is the teacher doing?

You might want to point out that any letter could be used in the expressions; the files just happen to use x.