Add/Subtract Like Denominators

Grade 4 · fractions · 64 practice problems · read aloud

🔊 Listen to this explanation

Adding & Subtracting Fractions with Like Denominators

🧠 What Is It & Why Is It Useful?

When fractions have the same denominator (the bottom number), it means they are describing parts of the same whole. For example, if you have 2 slices of a pizza cut into 8 pieces, and your friend gives you 1 more slice from the same pizza, you now have 3 slices. You just added fractions! This skill helps us combine or compare parts of things easily.

📝 Step-by-Step Guide

  1. Step 1: Look at the denominators. Are they the same? If YES, you're ready!
  2. Step 2: For addition, add the numerators (the top numbers). For subtraction, subtract the numerators.
  3. Step 3: Keep the denominator the same.
  4. Step 4: Simplify your answer if you can.

🔍 Visual Examples

Example 1: Addition

Add 2/7 + 3/7

  1. Denominators are the same (7).
  2. Add the numerators: 2 + 3 = 5.
  3. Keep the denominator: 5/7.
  4. Answer: 5/7

Example 2: Subtraction

Subtract 5/6 - 2/6

  1. Denominators are the same (6).
  2. Subtract the numerators: 5 - 2 = 3.
  3. Keep the denominator: 3/6.
  4. Simplify: 3/6 = 1/2.
  5. Answer: 1/2

⚠️ Common Mistakes

Adding the Denominators: Remember, the denominator tells us the size of the pieces. If you add them, you change the size of the whole, which is incorrect! Only add or subtract the numerators.

Forgetting to Simplify: Always check if your answer can be simplified. For example, 2/8 should be written as 1/4.

💡 Tips & Tricks

The "Pizza Slice" Rule: Imagine the denominator is the number of slices in one pizza. You can only add or subtract your slices (numerators) if the pizzas are the same size!

Rhyme to Remember: "If the bottoms are the same, just add or subtract the names (the top numbers). The bottom stays the game!"

🎯 How to Practice

  • Use fraction circles or pie charts to draw the problem.
  • Create your own problems with small denominators like 2, 4, 5, and 8.
  • Ask a friend or family member to give you two fractions to add or subtract.
  • Practice with online games that focus on "like denominators."

Practice problems

6 of the 64, worked through step by step — try them before opening the answer.

1 5/8 + 2/8 = ?

Hint: When fractions have the same bottom number, just add the top numbers together.

Show the answer

Answer: 7/8

  1. Identify the problem. We are adding two fractions: 5/8 and 2/8.
  2. Check the denominators. Both fractions have the same denominator, which is 8. When fractions have the same denominator, it means we are adding parts of the same size.
  3. Add the numerators. Since the denominators are the same, we keep the denominator and add the numerators together. Numerator: 5 + 2 = 7 Denominator: 8
  4. Write the result. Combining the new numerator with the denominator gives us the fraction 7/8.
  5. Check if the fraction can be simplified. The fraction 7/8 is already in its simplest form because 7 and 8 have no common factors other than 1. Final Answer: 7/8

2 5/8 + 3/8 = ?

Hint: When adding fractions with the same denominator, focus on what happens to the numerators while the denominator stays the same.

Show the answer

Answer: 1

  1. Identify the problem. We are adding two fractions: 5/8 and 3/8.
  2. Check the denominators. Both fractions have the same denominator, which is 8. When denominators are the same, we can add the fractions directly by adding the numerators.
  3. Add the numerators. The numerators are 5 and 3. 5 + 3 = 8. So, the new fraction is 8/8.
  4. Simplify the result. A fraction where the numerator and denominator are the same is equal to 1. 8/8 = 1.
  5. State the final answer. Therefore, 5/8 + 3/8 = 1.

3 3/5 + 4/5 = ?

Hint: When adding fractions with the same denominator, focus on what happens to the numerators.

Show the answer

Answer: 7/5

  1. Both fractions have the same denominator of 5.
  2. Add the numerators: 3 + 4 = 7.
  3. Keep the denominator the same: 7/5.

The answer is 7/5.

4 3/8 + 5/8 = ?

Hint: When adding fractions with the same denominator, focus on what happens to the numerators.

Show the answer

Answer: 1

  1. The fractions have the same denominator (8), so we add the numerators: 3 + 5 = 8.
  2. Write the sum over the common denominator: 8/8.
  3. Simplify the fraction: 8/8 = 1.

The answer is 1.

5 7/9 - 4/9 = ?

Hint: When subtracting fractions with the same denominator, focus on the numerators while keeping the denominator unchanged.

Show the answer

Answer: 1/3

  1. Both fractions have the same denominator (9), so we can subtract the numerators directly.
  2. Subtract the numerators: 7 - 4 = 3
  3. Write the result over the common denominator: 3/9
  4. Simplify the fraction by dividing numerator and denominator by their greatest common factor (3): 3 ÷ 3 = 1 and 9 ÷ 3 = 3
  5. The simplified fraction is 1/3

The answer is 1/3.

6 5/9 + 3/9 = ?

Hint: When adding fractions with the same denominator, focus on what happens to the numerators while keeping the denominator unchanged.

Show the answer

Answer: 8/9

  1. Identify the denominators - both fractions have denominator 9
  2. Add the numerators: 5 + 3 = 8
  3. Keep the same denominator: 8/9
  4. The fraction 8/9 is already in simplest form

The answer is 8/9.

Practise this topic — 10 free problems, no signup →