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# 2-2 Mental Math: Using Compatible Numbers and Compensation

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• ### 2-2 Mental Math: Using Compatible Numbers and Compensation

1. 1. 2-2 Mental Math: Using Compatible #s and Compensation Math Notes Mathematical Reasoning 1.0
2. 2. Compatible Numbers Compatible numbers are numbers that are easy to compute mentally. 19 + 25 + 11 = 30 + 25 = 55
3. 3. Compensation Numbers Compensation involves deciding which number to adjust to make it easier to add or subtract. Compensate by changing the other number. 47 + 16 Add 3 Subtract 3 to adjust 50 + 13 = 63
4. 4. Compensation Numbers Compensation involves deciding which number to adjust to make it easier to add or subtract. Compensate by changing the other number. 73 - 38 Add 2 Add 2 to adjust 75 - 40 = 35
5. 5. Guided Practice 9 + 1 + 25 = Any numbers you 9 + 1 = 10 can easily add FIRST to make this easier? 10 + 25 = __
6. 6. Guided Practice 9 + 1 + 25 =
7. 7. Guided Practice 9 + 1 + 25 = Any numbers you can easily add FIRST to make this easier?
8. 8. Guided Practice 9 + 1 + 25 = Any numbers you 9 + 1 = 10 can easily add FIRST to make this easier?
9. 9. Guided Practice 9 + 1 + 25 = Any numbers you 9 + 1 = 10 can easily add FIRST to make this easier? 10 + 25 = __
10. 10. Guided Practice 9 + 1 + 25 = Any numbers you 9 + 1 = 10 can easily add FIRST to make this easier? 35 10 + 25 = __
11. 11. Guided Practice 7 + 13 + 19 =
12. 12. Guided Practice 7 + 13 + 19 = Any numbers you can easily add FIRST to make this easier?
13. 13. Guided Practice 7 + 13 + 19 = Any numbers you 7 + 13 = 20 can easily add FIRST to make this easier?
14. 14. Guided Practice 7 + 13 + 19 = Any numbers you 7 + 13 = 20 can easily add FIRST to make this easier? 20 + 19 = __
15. 15. Guided Practice 7 + 13 + 19 = Any numbers you 7 + 13 = 20 can easily add FIRST to make this easier? 39 20 + 19 = __
16. 16. Guided Practice 29 + 37 =
17. 17. Guided Practice Remember, this is 29 + 37 = COMPENSATION with adding. ADD something, TAKE something away.
18. 18. Guided Practice +1 Remember, this is 29 + 37 = COMPENSATION with adding. ADD something, TAKE something away.
19. 19. Guided Practice +1 -1 Remember, this is 29 + 37 = COMPENSATION with adding. ADD something, TAKE something away.
20. 20. Guided Practice +1 -1 Remember, this is 29 + 37 = COMPENSATION with adding. ADD something, TAKE something away. 30
21. 21. Guided Practice +1 -1 Remember, this is 29 + 37 = COMPENSATION with adding. ADD something, TAKE something away. 30 36
22. 22. Guided Practice +1 -1 Remember, this is 29 + 37 = COMPENSATION with adding. ADD something, TAKE something away. 30 36 30 + 36 = __
23. 23. Guided Practice +1 -1 Remember, this is 29 + 37 = COMPENSATION with adding. ADD something, TAKE something away. 30 36 30 + 36 = 66 __
24. 24. Guided Practice 67 + 14 =
25. 25. Guided Practice Remember, this is 67 + 14 = COMPENSATION with adding. ADD something, TAKE something away.
26. 26. Guided Practice +3 Remember, this is 67 + 14 = COMPENSATION with adding. ADD something, TAKE something away.
27. 27. Guided Practice +3 -3 Remember, this is 67 + 14 = COMPENSATION with adding. ADD something, TAKE something away.
28. 28. Guided Practice +3 -3 Remember, this is 67 + 14 = COMPENSATION with adding. ADD something, TAKE something away. 70
29. 29. Guided Practice +3 -3 Remember, this is 67 + 14 = COMPENSATION with adding. ADD something, TAKE something away. 70 11
30. 30. Guided Practice +3 -3 Remember, this is 67 + 14 = COMPENSATION with adding. ADD something, TAKE something away. 70 11 70 + 11 = __
31. 31. Guided Practice +3 -3 Remember, this is 67 + 14 = COMPENSATION with adding. ADD something, TAKE something away. 70 11 81 70 + 11 = __
32. 32. Guided Practice 38 - 19 =
33. 33. Guided Practice Remember, this is 38 - 19 = COMPENSATION with subtracting. ADD something to BOTH numbers.
34. 34. Guided Practice +2 Remember, this is 38 - 19 = COMPENSATION with subtracting. ADD something to BOTH numbers.
35. 35. Guided Practice +2 +2 Remember, this is 38 - 19 = COMPENSATION with subtracting. ADD something to BOTH numbers.
36. 36. Guided Practice +2 +2 Remember, this is 38 - 19 = COMPENSATION with subtracting. ADD something to BOTH numbers. 40
37. 37. Guided Practice +2 +2 Remember, this is 38 - 19 = COMPENSATION with subtracting. ADD something to BOTH numbers. 40 21
38. 38. Guided Practice +2 +2 Remember, this is 38 - 19 = COMPENSATION with subtracting. ADD something to BOTH numbers. 40 21 40 - 21 = __
39. 39. Guided Practice +2 +2 Remember, this is 38 - 19 = COMPENSATION with subtracting. ADD something to BOTH numbers. 40 21 19 40 - 21 = __
40. 40. Guided Practice 89 - 37 =
41. 41. Guided Practice Remember, this is 89 - 37 = COMPENSATION with subtracting. ADD something to BOTH numbers.
42. 42. Guided Practice -4 Remember, this is 89 - 37 = COMPENSATION with subtracting. ADD something to BOTH numbers.
43. 43. Guided Practice -4 -4 Remember, this is 89 - 37 = COMPENSATION with subtracting. ADD something to BOTH numbers.
44. 44. Guided Practice -4 -4 Remember, this is 89 - 37 = COMPENSATION with subtracting. ADD something to BOTH numbers. 85
45. 45. Guided Practice -4 -4 Remember, this is 89 - 37 = COMPENSATION with subtracting. ADD something to BOTH numbers. 85 33
46. 46. Guided Practice -4 -4 Remember, this is 89 - 37 = COMPENSATION with subtracting. ADD something to BOTH numbers. 85 33 85 - 33 = __
47. 47. Guided Practice -4 -4 Remember, this is 89 - 37 = COMPENSATION with subtracting. ADD something to BOTH numbers. 85 33 85 - 33 = 52 __