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7.2 Adding and subtracting fractions

) Exercise 7.2

1 Work out these additions and subtractions.
Write each answer in its simplest form and as a mixed number when appropriate.
−
a 1 2 b 2 + 3 c 2 + 5 d 7 1 e 4 − 2 f 7 1
−
+
3 9 5 10 7 14 9 3 5 15 8 4
3
g 2 4 h 7 1 i 5 3 j 9 − k 4 2 l 13 3
−
+
+
+
−
3 5 9 2 6 4 10 4 5 3 20 8
2 Copy and complete these.
4
2
a 5 + 3 c 5 + 3 = 8 d 2 + 4 = + = , = 1 e 81+ = 9
3 5 3 5 15 15 15 15 15 15 15
3
5
b 5 − 3 c 23 23 d 23 23 = − = e = 1
−
−
4 6 4 6 4 6 1212 12 12 12
3 Work out these additions and subtractions.
Write each answer in its simplest form and as a mixed number when appropriate.
Show all the steps in your working.
3
7
1
a 2 3 + b 3 + 2 4 c 2 + 2 31
4 8 5 15 9 36
5
5
7
3
d 4 3 + e 15 + 2 f 4 + 5 3
4 7 8 10 6 5
1 23
4
g 3 − 9 h 2 − i 3 3 − 1 4
5 10 6 24 14 7
2
1
1
j 7 − 2 7 k 8 − 4 l 6 7 − 4 17
3 12 3 4 12 18
4 Read what Zalika says.
If I add together two fractions that are the
same, my answer will always be greater than 1.

Use at least two counter-examples
to show that this statement is not true.
5 Kwan is making a shelf from two pieces of wood.
1
4

The first piece is 1 m long; the second is 1 m long.
4 5 1 4
He fixes them on a wall, as shown in the diagram. 1 4 m 1 5 m

a What is the total length of the shelf?
b Show how to check your answer is correct.
3
6 Yun has a piece of silk 3 m long. 3
8 3 m
8
3
She cuts a piece of silk m long from the piece she has, to
4
give to her aunt.
2
Then she cuts a piece 1 m long from the piece she has left over,
3
to give to her sister.
2
a How long is the piece of silk that Yun has left? 3 m 1m m
3
4
b Show how to check your answer is correct.
7 Fractions 67