# Choosing the Correct Operation # When to do What

The first step in interpreting word problems is to understand what each of the four basic operations mean. Not knowing HOW to add, subtract, multiply, and divide- rather knowing WHEN.

## LEARN IT

The four basic operations are addition, subtraction, multiplication and division. It is crucial that you can correctly identify the appropriate operation in the real-world scenarios presented in GED word problems.

• Addition: Putting together, or totaling, any sized groups of the same kinds of things. For example: 5 apples and 3 apples equals 8 apples. 5+3=8

• Subtraction:

• Removing a group from a total. For example: Spending 5 out of 20 dollars leaves you with 15 dollars. 20-5=15

• Finding the difference between two numbers. For example: If John is 25 and Marti is 32, Marti is 7 years older than John. 32-25=7

• Multiplication:

• Putting together same sized groups to find a total. For example: Each student in a GED Class of 15 chips in \$5 for pizza for a total of \$75. 5(15)=75

• Scaling the size of a group. For example: A recipe calls for 4 eggs. John plans to make a half batch, so he only needs 2 eggs. 4(1/2)=2

• Division: Breaking a total into same sized groups. For example: A 4 1/2 foot board is sawed into 3/4 foot segments, resulting in 6 segments. 4 1/2 divided by 3/4 = 6

## PRACTICE IT Choosing the Correct Operation Beginner

### BEGINNING

Practice determining the appropriate operation and writing expressions. See examples #1-5 below. Choosing the Correct Operation Experienced

### EXPERIENCED

Use the givens and the appropriate operation to find the indicated information and write an appropriate expression. See examples #4- Challenge #2 below. Writing Algebraic Expressions

Apply the skill of choosing the correct operation to algebra by writing algebraic expressions from word problems. See Challenge #3-5 below.

## WORKED EXAMPLES

MathAbility- Inverse Operations

Beginning 1

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Experienced 1

Experienced 2