1. Adding Up

2. Category 1 Adding Up strategy :
The whole number is a multiple of ten or one hundred.
The subtrahend is close to a multiple of ten or a landmark number.

3. 20 – – – 9 20 – 8

4. 30 – – – – 12

5. 40 – – – – 19

6. 50 – – – – 24

7. 60 – – – – 29

8. 70 – – – – 34

9. 80 – – – – 39

10. 90 – – – – 44

11. 100 – – – – 44

12. Category 2 Adding Up strategy :
The whole number is a multiple of ten or one hundred.
The subtrahend is close to a multiple of ten or a landmark number.

13. 100 – – – – 37

14. 150 – – – 99

15. 250 – – – – 149

16. 300 – – – – 149

17. 400 – – – – 199

18. 500 – – – – 249

19. 750 – – – – 324

20. 1000 – – – – 499

21. Category 3 Adding Up strategy :
The whole number is NO longer an exact multiple of ten or one hundred.
The subtrahend is farther distance from the whole.

22. 50 – – – 37

23. 80 – – – – 36

24. 70 – – – – 39

25. 100 – – – – 83

26. 100 – – – – 89

27. 200 – – – – 198

28. 300 – – – – 287

29. 400 – – – – 298

30. 500 – – – – 671