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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 697 · 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. 1.44 + 29 =
  2. 2.18 + 9 =
  3. 3.621 + 99 =
  4. 4.51 + 29 =
  5. 5.49 + 9 =
  6. 6.63 + 29 =
  7. 7.72 + 19 =
  8. 8.78 + 9 =
  9. 9.22 + 29 =
  10. 10.649 + 99 =
  11. 11.59 − 9 =
  12. 12.25 + 9 =
  13. 13.34 + 9 =
  14. 14.84 − 9 =
  15. 15.21 + 29 =
  16. 16.260 + 99 =
  17. 17.17 + 9 =
  18. 18.43 − 19 =
  19. 19.30 + 29 =
  20. 20.276 − 99 =
  21. 21.30 + 19 =
  22. 22.82 − 9 =
  23. 23.108 − 29 =
  24. 24.76 − 19 =
  25. 25.41 − 9 =
  26. 26.416 + 99 =
  27. 27.41 − 29 =
  28. 28.30 + 9 =
  29. 29.20 + 29 =
  30. 30.43 + 29 =
  31. 31.584 + 99 =
  32. 32.629 + 99 =
  33. 33.135 + 99 =
  34. 34.35 − 29 =
  35. 35.762 + 99 =
  36. 36.484 − 99 =
  37. 37.299 + 99 =
  38. 38.668 − 99 =
  39. 39.772 − 99 =
  40. 40.79 − 29 =

Answer key

  1. 73
  2. 27
  3. 720
  4. 80
  5. 58
  6. 92
  7. 91
  8. 87
  9. 51
  10. 748
  11. 50
  12. 34
  13. 43
  14. 75
  15. 50
  16. 359
  17. 26
  18. 24
  19. 59
  20. 177
  21. 49
  22. 73
  23. 79
  24. 57
  25. 32
  26. 515
  27. 12
  28. 39
  29. 49
  30. 72
  31. 683
  32. 728
  33. 234
  34. 6
  35. 861
  36. 385
  37. 398
  38. 569
  39. 673
  40. 50

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