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When we add two fractions, they must have the same denominator.
We use equivalent fractions to change them into two fractions with the same lowest common denominator.
Example
Work out
3 | + | 1 |
10 | 15 |
Answer
We must first find the lowest common multiple of 10 and 15, which is 30.
Then we change each fraction into 30ths.
30 ÷ 10 = 3 so we multiply top and bottom of the first fraction by 3.
30 ÷ 15 = 2 so we multiply top and bottom of the second fraction by 2.
3 | + | 1 |
10 | 15 |
= | 3 × 3 | + | 1 × 2 |
10 × 3 | 15 × 2 |
= | 9 | + | 2 |
30 | 30 |
= | 11 |
30 |
We must always simplify or reduce our answer to its lowest possible terms.
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When we add two fractions, they must have the same denominator.
We use equivalent fractions to change them into two fractions with the same lowest common denominator.
Example
Work out
3 | + | 1 |
10 | 15 |
Answer
We must first find the lowest common multiple of 10 and 15, which is 30.
Then we change each fraction into 30ths.
30 ÷ 10 = 3 so we multiply top and bottom of the first fraction by 3.
30 ÷ 15 = 2 so we multiply top and bottom of the second fraction by 2.
3 | + | 1 |
10 | 15 |
= | 3 × 3 | + | 1 × 2 |
10 × 3 | 15 × 2 |
= | 9 | + | 2 |
30 | 30 |
= | 11 |
30 |
We must always simplify or reduce our answer to its lowest possible terms.
Question
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Teacher explanation