Adding and subtracting fractions

The Maths Habit

Ria says 12 + 13 = 25.
How can you tell she is wrong without working it out?

25 is less than 12

What is the missing number?

  1. 23 = ?12

    8

  2. 35 = ?15

    9

  3. 14 = ?20

    5

  4. 56 = ?18

    15

Denominator
The bottom number of a fraction. It tells you how many equal parts the whole is cut into.
Common denominator
A denominator that both fractions can share.

13
12

What is a common denominator?

13 and 15 15

Work out 15 + 23

15
↓
23
↓
=
15 = 315,  23 = 1015
315 + 1015 = 1315  Answer1315

Work out 14 + 25

14
↓
25
↓
=
14 = 520,  25 = 820
520 + 820 = 1320  Answer1320

Work out 15 + 23

15
↓
23
↓
=
15 = 315,  23 = 1015
315 + 1015 = 1315  Answer1315

Work out 27 + 12

27
↓
12
↓
=
27 = 414,  12 = 714
414 + 714 = 1114  Answer1114

Give your answer in its simplest form

56 − 13

Work out 34 − 25

34
↓
25
↓
=
34 = 1520,  25 = 820
1520 − 820 = 720  Answer720

Work out 23 − 14

23
↓
14
↓
=
23 = 812,  14 = 312
812 − 312 = 512  Answer512

Work out 34 − 25

34
↓
25
↓
=
34 = 1520,  25 = 820
1520 − 820 = 720  Answer720

Work out 56 − 38

56
↓
38
↓
=
56 = 2024,  38 = 924
2024 − 924 = 1124  Answer1124

Work out 34 − 25

34
↓
25
↓
=
34 = 1520,  25 = 820
1520 − 820 = 720  Answer720

Work out 38 + 13

38
↓
13
↓
=
38 = 924,  13 = 824
924 + 824 = 1724  Answer1724

Work out 34 − 25

34
↓
25
↓
=
34 = 1520,  25 = 820
1520 − 820 = 720  Answer720

Work out 79 − 16

79
↓
16
↓
=
79 = 1418,  16 = 318
1418 − 318 = 1118  Answer1118

Work out 34 − 25

34
↓
25
↓
=
34 = 1520,  25 = 820
1520 − 820 = 720  Answer720

Work out 16 + 58

16
↓
58
↓
=
16 = 424,  58 = 1524
424 + 1524 = 1924  Answer1924

Adding and subtracting fractions worksheet, page 1

Adding and subtracting fractions worksheet, page 2

Answer sheet

  1. Zed reads 13 of a book on Monday and 25 of it on Tuesday. What fraction of the book is left to read?

    415

  2. Find two fractions with different denominators that add up to 12.

    13 + 16

  1. Work out 14 + 23

    1112

  2. Work out 56 − 14. Give your answer in its simplest form.

    712

  3. Work out 310 + 16. Give your answer in its simplest form.

    715

  4. Ali says 23 + 15 = 38. Is Ali right? Explain how you know.

    No: 1315
Exit tickets to print