Page 82 - Mathematics Coursebook

7.5 Adding and subtracting fractions

7.5 Adding and subtracting fractions

To add or subtract fractions you want the denominators to be the same.

When you add or subtract fractions follow these steps.
t If the denominators are the same, simply add or subtract the numerators. Once the denominators

t If the denominators are di%erent, write the fractions as equivalent are the same, add the
fractions with the same denominator, then add or subtract the numerators. numerators but do not
t Cancel your answer to its simplest form. add the denominators.
t If your answer is an improper fraction, write it as a mixed number.

Worked example 7.5
4 3 7 5 5 1
Work these out. a 5 − 5 b 8 + 8 c 6 + 3

4 − 3 1
a 5 = 5 The denominators are the same, so simply subtract the numerators.

+
75 12
b 8 = 8 The denominators are the same, so simply add the numerators.
12 = 1 4 12 is an improper fraction, so re-write it as a mixed number.
8 8 8
4 1 4
1 8 = 1 2 Finally, cancel the 8 to its simplest form.

c 5 + 1 = 5 + 2 The denominators are not the same so change the 1 3 into 2 .
6
6 3 6 6
+
52 = 7 The denominators are now the same, so add the numerators.
6 6
7 1 7
= 1 is an improper fraction, so re-write it as a mixed number.
6 6 6

) Exercise 7.5

1 Work these out.
a 1 + 2 b 3 + 3 c 5 − 2 d 8 − 4
5 5 7 7 7 7 9 9

2 Work out these additions. Write each answer in its simplest form and as a mixed number.
a 3 + 3 b 3 + 7 c 9 + 7 d 11 + 5
4 4 8 8 10 10 14 14

3 Work out the answers to these additions.
Write each answer in its simplest form and as a mixed number.
4 13 5 11 3 13 5 11
a + b + c + d +
5 20 8 16 7 14 6 18
4 Mia adds together two proper fractions. The fractions have different denominators.
2
She gets an answer of 1 .
5
Write down two fractions that Mia may have added.

7 Fractions 81