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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 28 · 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. 1.26 − 19 =
  2. 2.65 + 9 =
  3. 3.782 − 99 =
  4. 4.54 − 29 =
  5. 5.34 − 19 =
  6. 6.46 + 29 =
  7. 7.50 + 29 =
  8. 8.622 + 99 =
  9. 9.58 + 19 =
  10. 10.17 + 19 =
  11. 11.81 − 29 =
  12. 12.79 − 29 =
  13. 13.162 + 99 =
  14. 14.67 − 19 =
  15. 15.18 + 19 =
  16. 16.70 + 19 =
  17. 17.12 − 9 =
  18. 18.415 + 99 =
  19. 19.77 − 29 =
  20. 20.47 + 19 =
  21. 21.794 − 99 =
  22. 22.784 + 99 =
  23. 23.71 − 29 =
  24. 24.77 − 19 =
  25. 25.313 + 99 =
  26. 26.25 + 9 =
  27. 27.416 + 99 =
  28. 28.298 − 99 =
  29. 29.40 + 29 =
  30. 30.70 + 9 =
  31. 31.12 + 9 =
  32. 32.799 − 99 =
  33. 33.93 − 29 =
  34. 34.247 − 99 =
  35. 35.59 − 29 =
  36. 36.50 + 19 =
  37. 37.13 + 29 =
  38. 38.43 − 9 =
  39. 39.47 + 29 =
  40. 40.98 − 19 =

Answer key

  1. 7
  2. 74
  3. 683
  4. 25
  5. 15
  6. 75
  7. 79
  8. 721
  9. 77
  10. 36
  11. 52
  12. 50
  13. 261
  14. 48
  15. 37
  16. 89
  17. 3
  18. 514
  19. 48
  20. 66
  21. 695
  22. 883
  23. 42
  24. 58
  25. 412
  26. 34
  27. 515
  28. 199
  29. 69
  30. 79
  31. 21
  32. 700
  33. 64
  34. 148
  35. 30
  36. 69
  37. 42
  38. 34
  39. 76
  40. 79

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