Grade 4 (age 9-10)

grade 4 Fraction Addition & Subtraction

Fraction Addition & Subtraction

When two fractions share a denominator, adding and subtracting stay simple. You keep that denominator and only add or subtract the numerators. Cut a cake into 6 slices, eat 2 and let a friend eat 3, and 2/6 plus 3/6 is 5/6. The denominator is the size of a slice, so do not add those bottoms; switch add and subtract and the bars and the equation show each step.

Adding Fractions with Same Denominator

🍰 Think of a cake!

①A cake was cut into 6 slices

②I ate 2, my friend ate 3

③Together: 2/6 + 3/6 = 5/6

④Denominator (slice size) stays, only numerators (count) add!

Fractions with Bars

Denominator (same size)6

First numerator2

Second numerator3

Check with Formulas

💡 Rule for Same-Denominator Fractions

①Same denominator: add or subtract only the numerators. In the formula, a and b are numerators, c is the denominator

②Never add or subtract denominators!

③Simplifying means dividing numerator and denominator by the same number. Example: 2/4 = 1/2

④The sliders keep the sum from going over 1

Summary

Adding Same-Denominator

ac + bc = a+bc

Denominator stays, add only numerators

Subtracting Same-Denominator

ac − bc = a−bc

Denominator stays, subtract only numerators

Watch Out!

Don't add denominators!

Denominator is 'slice size' — it doesn't change

🎯 Key Points

①Same denominator: only operate on numerators

②Never add/subtract denominators

③This page keeps the sum at 1 or less. Writing a mixed number when the sum is greater than 1 comes later

④Simplify by dividing by the same number. 2/4 = 1/2

⑤Later, learn fractions with different denominators!

Examples and Unit Test

Example 1

Calculate 2/7 + 3/7.

The denominators are both 7, so add only the numerators: 2 + 3 = 5.

The denominator stays 7, so the answer is 5/7.

▸ 57 (five-sevenths)

For same-denominator fractions, keep the denominator and add only the numerators.

Example 2

Calculate 5/8 − 2/8.

The denominators are both 8, so subtract only the numerators: 5 − 2 = 3.

The denominator stays 8, so the answer is 3/8.

▸ 38 (three-eighths)

For subtraction too, keep the denominator and subtract only the numerators.

Unit Test

What is the value of 1/6 + 4/6?

①512

②56

③46

④536

▸ ② 56

Same denominator, so add the numerators: 1 + 4 = 5.

The denominator 6 stays, so it is 5/6. (Never add denominators!)

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Multi-digit Multiplication

Understanding Decimals