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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 495 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.12 + 19 =
  2. 2.66 + 19 =
  3. 3.57 + 9 =
  4. 4.76 + 9 =
  5. 5.67 − 29 =
  6. 6.852 − 99 =
  7. 7.47 + 19 =
  8. 8.85 − 19 =
  9. 9.52 − 9 =
  10. 10.79 − 9 =
  11. 11.71 + 9 =
  12. 12.19 + 19 =
  13. 13.31 + 29 =
  14. 14.77 + 9 =
  15. 15.50 + 29 =
  16. 16.717 + 99 =
  17. 17.570 + 99 =
  18. 18.314 + 99 =
  19. 19.315 − 99 =
  20. 20.49 + 19 =
  21. 21.60 + 9 =
  22. 22.83 − 9 =
  23. 23.266 − 99 =
  24. 24.102 − 29 =
  25. 25.353 + 99 =
  26. 26.46 + 9 =
  27. 27.121 + 99 =
  28. 28.20 + 19 =
  29. 29.79 + 19 =
  30. 30.412 − 99 =
  31. 31.738 + 99 =
  32. 32.159 + 99 =
  33. 33.18 − 9 =
  34. 34.59 − 19 =
  35. 35.65 + 29 =
  36. 36.73 + 29 =
  37. 37.763 + 99 =
  38. 38.90 − 29 =
  39. 39.49 − 19 =
  40. 40.84 − 29 =

Answer key

  1. 31
  2. 85
  3. 66
  4. 85
  5. 38
  6. 753
  7. 66
  8. 66
  9. 43
  10. 70
  11. 80
  12. 38
  13. 60
  14. 86
  15. 79
  16. 816
  17. 669
  18. 413
  19. 216
  20. 68
  21. 69
  22. 74
  23. 167
  24. 73
  25. 452
  26. 55
  27. 220
  28. 39
  29. 98
  30. 313
  31. 837
  32. 258
  33. 9
  34. 40
  35. 94
  36. 102
  37. 862
  38. 61
  39. 30
  40. 55

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