# Adding fractions

To add fractions, first make the bottom numbers (denominators) the same, then add the top numbers (numerators).

Maths (school) · Part 01: Number and ratio · Card 2 of 9 · Last updated 2026-10-19

## Analogy

You cannot add thirds and quarters until you cut both pizzas into twelfths.

## Example

**1/3 + 1/4**

1/3 = 4/12
1/4 = 3/12
4/12 + 3/12 = 7/12

## In practice

Recipes often mix amounts like 1/2 cup and 1/3 cup, and you need a common denominator to total them.

## Practice

### Flashcards

- **What is 1/3 + 1/4?** 7/12. Both become twelfths: 4/12 + 3/12.

## Questions people ask

### How do you find a common denominator?

Find a number that both bottom numbers divide into. The easiest choice is often the two numbers multiplied together. For 1/3 and 1/4, 12 works. A smaller shared multiple, called the lowest common multiple, keeps the numbers smaller, but any shared multiple gives the right answer.

### Do you add the denominators when adding fractions?

No. The denominator tells you the size of each piece, and that stays the same. Only the numerators are added. So 3/8 + 2/8 = 5/8, not 5/16. You are counting how many eighths you have, and eighths remain eighths.

## Related concepts

- [BIDMAS](https://studyvisually.com/learn/science/maths-school/maths-school-part-1/maths-school-part-1-concept-1)
- [Percentage of an amount](https://studyvisually.com/learn/science/maths-school/maths-school-part-1/maths-school-part-1-concept-3)
- [Percentage change](https://studyvisually.com/learn/science/maths-school/maths-school-part-1/maths-school-part-1-concept-4)
- [Laws of indices](https://studyvisually.com/learn/science/maths-school/maths-school-part-1/maths-school-part-1-concept-7)

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