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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 221 · 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. 1.25 − 19 =
  2. 2.60 + 9 =
  3. 3.30 − 19 =
  4. 4.77 + 29 =
  5. 5.35 − 19 =
  6. 6.40 − 9 =
  7. 7.56 + 9 =
  8. 8.18 − 9 =
  9. 9.64 + 29 =
  10. 10.638 − 99 =
  11. 11.14 + 29 =
  12. 12.26 − 9 =
  13. 13.56 + 29 =
  14. 14.13 − 9 =
  15. 15.374 + 99 =
  16. 16.68 + 9 =
  17. 17.63 − 19 =
  18. 18.526 + 99 =
  19. 19.76 + 9 =
  20. 20.77 + 19 =
  21. 21.98 − 19 =
  22. 22.57 − 29 =
  23. 23.13 + 9 =
  24. 24.155 − 99 =
  25. 25.311 − 99 =
  26. 26.24 − 9 =
  27. 27.78 − 29 =
  28. 28.651 + 99 =
  29. 29.684 − 99 =
  30. 30.81 − 9 =
  31. 31.15 + 19 =
  32. 32.89 − 19 =
  33. 33.32 − 9 =
  34. 34.68 − 9 =
  35. 35.62 − 9 =
  36. 36.57 − 19 =
  37. 37.797 − 99 =
  38. 38.78 + 19 =
  39. 39.78 + 9 =
  40. 40.91 − 29 =

Answer key

  1. 6
  2. 69
  3. 11
  4. 106
  5. 16
  6. 31
  7. 65
  8. 9
  9. 93
  10. 539
  11. 43
  12. 17
  13. 85
  14. 4
  15. 473
  16. 77
  17. 44
  18. 625
  19. 85
  20. 96
  21. 79
  22. 28
  23. 22
  24. 56
  25. 212
  26. 15
  27. 49
  28. 750
  29. 585
  30. 72
  31. 34
  32. 70
  33. 23
  34. 59
  35. 53
  36. 38
  37. 698
  38. 97
  39. 87
  40. 62

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