Adding-And-Subtracting-Fractions- Wjec-Eduqas Foundation

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Exam code:C300

Adding & subtracting fractions

How do I add or subtract two fractions?

Addition and subtraction are treated in exactly the same way when dealing with fractions
- Find the lowest common denominator
- Write each fraction as an equivalent fraction over this denominator
- Add (or subtract) the numerators and write this over a single denominator
  - Do not add the denominators
- Simplify the fraction by cancelling common factors

What do I do if any of the fractions are mixed numbers?

Convert any mixed numbers into improper fractions
- Add or subtract the fractions as usual
- Remember to convert the answer back to a mixed number if required

Worked Example

(a) Find $2 over 3 plus 1 fifth$ .

Find the lowest common denominator of 3 and 5
15 is the smallest number that can be divided by both 3 and 5

The lowest common denominator is 15

Write both fractions as equivalent fractions with a common denominator of 15
Multiply the numerator and denominator of the first fraction by 5
Multiply the numerator and denominator of the second fraction by 3

$fraction numerator 2 cross times 5 over denominator 3 cross times 5 end fraction plus fraction numerator 1 cross times 3 over denominator 5 cross times 3 end fraction equals 10 over 15 plus 3 over 15$

Add the numerators and write over a single denominator

$fraction numerator 10 plus 3 over denominator 15 end fraction equals 13 over 15$

There are no common factors that will cancel

$bold 13 over bold 15$

(b) F

Maths Gcse Wjec-Eduqas Foundation

Adding-And-Subtracting-Fractions- Wjec-Eduqas Foundation

Adding & subtracting fractions

How do I add or subtract two fractions?

What do I do if any of the fractions are mixed numbers?

Worked Example

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