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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 870 · 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. 1.55 − 29 =
  2. 2.56 − 9 =
  3. 3.60 + 19 =
  4. 4.74 + 9 =
  5. 5.27 − 9 =
  6. 6.28 + 19 =
  7. 7.324 − 99 =
  8. 8.77 + 29 =
  9. 9.76 + 29 =
  10. 10.50 − 29 =
  11. 11.67 + 9 =
  12. 12.80 − 9 =
  13. 13.289 − 99 =
  14. 14.40 + 29 =
  15. 15.80 − 29 =
  16. 16.49 − 9 =
  17. 17.687 − 99 =
  18. 18.17 + 19 =
  19. 19.409 + 99 =
  20. 20.71 − 9 =
  21. 21.256 + 99 =
  22. 22.64 − 29 =
  23. 23.13 + 9 =
  24. 24.19 + 29 =
  25. 25.659 − 99 =
  26. 26.26 + 29 =
  27. 27.48 + 19 =
  28. 28.23 + 19 =
  29. 29.74 − 9 =
  30. 30.16 − 9 =
  31. 31.418 + 99 =
  32. 32.32 + 9 =
  33. 33.36 − 9 =
  34. 34.75 + 9 =
  35. 35.31 + 29 =
  36. 36.45 − 29 =
  37. 37.75 + 19 =
  38. 38.230 − 99 =
  39. 39.712 − 99 =
  40. 40.410 + 99 =

Answer key

  1. 26
  2. 47
  3. 79
  4. 83
  5. 18
  6. 47
  7. 225
  8. 106
  9. 105
  10. 21
  11. 76
  12. 71
  13. 190
  14. 69
  15. 51
  16. 40
  17. 588
  18. 36
  19. 508
  20. 62
  21. 355
  22. 35
  23. 22
  24. 48
  25. 560
  26. 55
  27. 67
  28. 42
  29. 65
  30. 7
  31. 517
  32. 41
  33. 27
  34. 84
  35. 60
  36. 16
  37. 94
  38. 131
  39. 613
  40. 509

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