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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 102 · 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. 1.42 − 29 =
  2. 2.33 − 9 =
  3. 3.48 + 9 =
  4. 4.71 − 29 =
  5. 5.451 − 99 =
  6. 6.62 + 9 =
  7. 7.89 − 19 =
  8. 8.81 − 29 =
  9. 9.38 + 29 =
  10. 10.38 − 29 =
  11. 11.653 − 99 =
  12. 12.73 + 29 =
  13. 13.32 − 29 =
  14. 14.556 + 99 =
  15. 15.79 + 9 =
  16. 16.65 + 29 =
  17. 17.45 − 19 =
  18. 18.644 + 99 =
  19. 19.633 + 99 =
  20. 20.43 + 19 =
  21. 21.35 + 19 =
  22. 22.46 + 29 =
  23. 23.109 − 29 =
  24. 24.78 + 19 =
  25. 25.38 + 19 =
  26. 26.30 + 19 =
  27. 27.435 − 99 =
  28. 28.50 + 9 =
  29. 29.70 + 29 =
  30. 30.72 + 29 =
  31. 31.382 + 99 =
  32. 32.28 − 19 =
  33. 33.37 + 29 =
  34. 34.516 + 99 =
  35. 35.23 − 9 =
  36. 36.50 − 19 =
  37. 37.40 − 29 =
  38. 38.27 + 19 =
  39. 39.28 + 19 =
  40. 40.786 − 99 =

Answer key

  1. 13
  2. 24
  3. 57
  4. 42
  5. 352
  6. 71
  7. 70
  8. 52
  9. 67
  10. 9
  11. 554
  12. 102
  13. 3
  14. 655
  15. 88
  16. 94
  17. 26
  18. 743
  19. 732
  20. 62
  21. 54
  22. 75
  23. 80
  24. 97
  25. 57
  26. 49
  27. 336
  28. 59
  29. 99
  30. 101
  31. 481
  32. 9
  33. 66
  34. 615
  35. 14
  36. 31
  37. 11
  38. 46
  39. 47
  40. 687

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