2. Today we will be learning to work out answers to calculations by using: what we already know about addition and subtraction patterns of similar calculations.

3. Mental Activity We are going to practise adding and subtracting numbers up to 20.

4. What number do you need to add to each card to make 20?

5. 911

6. 128

7. 713

8. 164

9. 155

10. 317

11. You have to make 12. Work in a group. Take a number card from 0 to 20. Choose a partner with a number that you can add or subtract from your number to make 12.

12. I have 8 My partner has 4 8 + 4 = 12 Example:

13. Now find a partner to make 15. Now find a partner to make 16. Now find a partner to make 18. Now find a partner to make 19.

14. Main Activity Today we will use what we already know to help us to work out other number facts.

15. 70 + 70 = What do we already know that could help us to work this out?

16. 70 + 70 = Double 7 = 14 70 is ten times bigger than 7 Double 70 will be ten times bigger than 14 140 Double 70 = 140

17. Let’s try some more… Can you say the easy double fact you use to find the answer? Addition Double fact 60 + 60 =120 40 + 40 =80 6 + 6 =12 4 + 4 = 8 80 + 80 =160 8 + 8 = 16

18. Work with a partner. Double all the multiples of 10 to 100. 100 90 80 70 60 50 40 30 20 10 DoubleNumber 20 40 60 80 100 120 140 160 180 200

19. What number knowledge would you use to work out this calculation? 8 + 4 = 12 so 80 + 40 = 120 80 + 40 =

20. Group Work Adding and subtracting work Work on number chains