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Maths

Fractions

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Adding and subtracting

It is hard to picture what the answer is if you add 1/2 and 1/3. Rewriting the fractions with a common bottom number (in this case, 6) makes it easier to see the answer.

Remember: You can only add and subtract fractions when the bottom numbers are the same.

So to add or subtract fractions:

  1. Change the fractions so they have the same bottom number.
  2. Add or subtract the top numbers.

Example

1/2 + 1/3 = 3/6 + 2/6 = 5/6

7/10 - 2/5 = 7/10 - 4/10 = 3/10

Question

What is 1/4 + 1/3 = ?

Answer

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

Mixed numbers

To add or subtract mixed numbers, it is usually easiest to change them to improper fractions first:

Question

3 1/3 + 4 1/2 = ?

Answer

3 1/3 + 4 1/2 = 10/3 + 9/2 = 20/6 + 27/6 = 47/6 = 7 5/6

Activity

Fractions activity

Denominator? Numerator? Find out what it's all about in this activity!

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