4/12 + 9/12 − 4/12 = □ Answer in simplest form

3/4. Keep the bottom and work the tops left to right, 4 + 9 − 4, then simplify.

3/6 + 2/6 − 3/6 = 8/6 True or false?

False. Tops left to right: 3 + 2 − 3 = 2, so the answer is 2/6.

8/12 + □/12 − 5/12 = 12/12. What is □?

9. Look at the tops: 8 + □ − 5 = 12, so □ = 12 + 5 − 8 = 9.

中文

Improper fractions, mixed numbers and like fractions · Usually met around P4

Three like fractions

Keep the bottom; work the tops left to right.

How to do it

Method

Keep the bottom; work the tops left to right

29 + 59 − 49 = 39 = 13

Another way

Count the ninths

2 + 5 − 4 = 3 ninths

In full

To add and take away like fractions, keep the bottom and work with the tops: 29 + 59 − 49 = (2 + 5 − 4)/9 = 39 = 13. With adding and taking away together, work left to right: don't do a later add first. Give the answer in simplest form. Or think in ninths: 2 ninths and 5 ninths, take away 4 ninths, leaves 3 ninths. Careful: bottoms never add, so 29 + 59 is not 718.

Worked examples

Have a go first, then open each one for the answer and the working.

Example 1
412 + 912 − 412 = □
Answer in simplest form
Show the answer and working
Answer: 34
Keep the bottom and work the tops left to right, 4 + 9 − 4, then simplify.
Example 2
36 + 26 − 36 = 86
True or false?
Show the answer and working
Answer: False
Tops left to right: 3 + 2 − 3 = 2, so the answer is 26.
Example 3
812 + □/12 − 512 = 1212. What is □?
Show the answer and working
Answer: 9
Look at the tops: 8 + □ − 5 = 12, so □ = 12 + 5 − 8 = 9.

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