Adding Mixed Numbers with Different Denominators: Step-by-Step Example
22 October 2026
When children are learning to add mixed numbers with different denominators, it can seem tricky at first. Breaking the process into simple steps helps them see how to work with both the whole numbers and the fractions.
Worked example
Add 1 1/4 + 2 2/3
Step 1: Add the whole numbers.
1 + 2 = 3
Step 2: Find a common denominator for the fractions.
The denominators are 4 and 3. The lowest common denominator is 12.
Step 3: Convert the fractions to have the same denominator.
1/4 = 3/12 2/3 = 8/12
Step 4: Add the fractions.
3/12 + 8/12 = 11/12
Step 5: Combine the whole number and the fraction.
3 + 11/12 = 3 11/12
The correct answer is 3 11/12.
| Step | Working | Result |
|---|---|---|
| Add whole numbers | 1 + 2 | 3 |
| Find common denominator | 4 and 3 → 12 | 12 |
| Convert fractions | 1/4 = 3/12, 2/3 = 8/12 | 3/12, 8/12 |
| Add fractions | 3/12 + 8/12 | 11/12 |
| Combine | 3 + 11/12 | 3 11/12 |
Key insight: Once your child has seen how to add mixed numbers with different denominators, they will start to notice the importance of finding a common denominator. This skill is useful for many fraction questions in 11+ maths. Now, your child can try a similar question to build confidence.
