Can you do maths in your head? Here are some clever tricks to help you work out sums quickly.
Trick 1: One more and one less
Adding 1 gives the next number. Taking away 1 gives the number before.
15 + 1 = 16 15 − 1 = 14
Trick 2: Zero changes nothing
8 + 0 = 8 8 − 0 = 8
Trick 3: Make ten
These pairs make 10. Learn them by heart!
| Pair | Makes |
|---|---|
| 0 + 10 | 10 |
| 1 + 9 | 10 |
| 2 + 8 | 10 |
| 3 + 7 | 10 |
| 4 + 6 | 10 |
| 5 + 5 | 10 |
| 6 + 4 | 10 |
| 7 + 3 | 10 |
| 8 + 2 | 10 |
| 9 + 1 | 10 |
| 10 + 0 | 10 |
To add 8 + 5: take 2 from the 5 to make 10. 8 + 2 = 10. Then 10 + 3 = 13.
Trick 4: Count on or count back
For 14 + 3, start at 14 and count on: 15, 16, 17. For 14 − 3, count back: 13, 12, 11.
Trick 5: Fact families
If you know 6 + 4 = 10, you also know:
- 4 + 6 = 10
- 10 − 4 = 6
- 10 − 6 = 4
TRY ITQuick maths: 10 questions
Work it out in your head. Tap the answer. Can you get 10 out of 10?
Let’s practise
Try each one. Then tap Show answer to check.
1. 19 + 1 = ☐
Show answer
20. The next number.
2. 12 − 1 = ☐
Show answer
11. The number before.
3. 13 + 0 = ☐
Show answer
13.
4. 7 + ☐ = 10
Show answer
3.
5. 9 + 4 = ☐ (make ten first)
Show answer
9 + 1 = 10, then 10 + 3 = 13.
6. You know 8 + 3 = 11. So 11 − 3 = ☐
Show answer
8.
7. 16 − 2 = ☐ (count back)
Show answer
15, 14. The answer is 14.
Quick check
1. What is 5 + 5?
Show answer
10.
2. What is 20 − 0?
Show answer
20.
3. Which number goes with 6 to make 10?
Show answer
4.
Maths words
Say these words with a grown-up. Can you use each one in a sentence?
add · take away · next number · number before · zero · make ten · double · fact family
Try it at home
- Play “Make 10” with your fingers: a grown-up shows some fingers and you show the rest.
- In the car or taxi, ask quick questions like “What is one more than 14?”
- Write a fact family on a card and stick it on the fridge.
For parents and teachers
After this lesson, your child should be able to:
- recall addition and subtraction facts up to 20
- use one more / one less as the next and previous number
- add and take away zero
- use “make ten”, counting on and counting back to work things out
- use a known fact to find related facts (for example 6 + 4 = 10, so 10 − 4 = 6)
A few minutes of quick-fire questions each day works better than one long session.
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Next: Solid and Flat Shapes
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