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Cambridge / IGCSE • Fractions Operations

Adding Fractions with Unlike Denominators

To add fractions, they must have the same unit size (denominator).

Learning Objectives

  • Find a common denominator for two fractions
  • Convert fractions to equivalent fractions with common denominators
  • Add numerators and simplify the answer

Lesson Explanation

Lesson Content

Find the Least Common Multiple (LCM) of the denominators. Convert both fractions so they share this common denominator, then add the numerators.

💡 Key Takeaway

Take one step at a time, check your working carefully, and keep both sides balanced!

Worked Examples

Example 1

Add 1/3 + 1/4

  1. Step 1

    Find common denominator of 3 and 4: 12

  2. Step 2

    Convert fractions: 1/3 = 4/12 and 1/4 = 3/12

  3. Step 3

    Add numerators: 4/12 + 3/12 = 7/12

Visual Method

Balance Every Step

Mathematics becomes much clearer when you can see the structure behind equations.

Watch Video Explanation

Practice Questions

Try solving each question on paper first. Tap below to check a helpful hint or solution!

Question 1

Add 1/2 + 2/5

Show Hint / Solution 💡

Common denominator is 10.

Question 2

Add 2/3 + 1/6

Show Hint / Solution 💡

Convert 2/3 to denominator 6.

Lesson Summary

What to Remember

Always find a common denominator before adding fractions!

Download Lesson Notes ↓