Adding & Subtracting Fractions

Grade 4 Mathematics

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Date:

The Big Idea

When fractions have the SAME denominator (like denominators), we can add or subtract them easily!

Add or subtract the NUMERATORS (top numbers).

Keep the DENOMINATOR the same (bottom number).

Then simplify if you can!

Example 1: Adding Fractions

28 + 38 = ?

2/8
+ 3/8
= 5/8
1

Check: Are the denominators the same? YES! Both are 8ths.

2

Add the numerators: 2 + 3 = 5

3

Keep the denominator: 8

28 + 38 = 58

Example 2: Subtracting Fractions

56 - 26 = ?

Start: 5/6
Take away 2/6
= 3/6 = 1/2
1

Subtract the numerators: 5 - 2 = 3

2

Keep the denominator: 6

3

Simplify! 3/6 = 1/2 (divide both by 3)

TRAP ALERT: Don't Add the Denominators!

WRONG: 1/4 + 2/4 = 3/8 (Don't add 4 + 4!)

RIGHT: 1/4 + 2/4 = 3/4 (Only add the numerators: 1 + 2 = 3. The denominator stays 4!)

Example 3: Mixed Numbers

215 + 135 = ?

1

Add the whole numbers: 2 + 1 = 3

2

Add the fractions: 1/5 + 3/5 = 4/5

3

Combine: 3 + 4/5 = 3 4/5

Your Turn: Add and Subtract

1. Add the fractions.

38 + 48 =

2. Subtract the fractions. Simplify your answer.

710 - 310 = =

3. Add the mixed numbers.

126 + 236 =

4. Word Problem: Jenna drank 2/5 of a bottle of water. Later, she drank another 2/5. What fraction of the bottle did she drink in all?

Equation:

Answer: of the bottle

Remember!