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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 222 · 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. 1.484 + 99 =
  2. 2.77 + 19 =
  3. 3.80 − 9 =
  4. 4.20 + 19 =
  5. 5.83 − 19 =
  6. 6.12 + 9 =
  7. 7.16 + 19 =
  8. 8.443 + 99 =
  9. 9.74 − 9 =
  10. 10.529 + 99 =
  11. 11.416 + 99 =
  12. 12.26 + 29 =
  13. 13.23 + 19 =
  14. 14.97 − 29 =
  15. 15.20 − 9 =
  16. 16.75 + 19 =
  17. 17.49 − 29 =
  18. 18.898 − 99 =
  19. 19.60 − 9 =
  20. 20.45 + 29 =
  21. 21.60 + 9 =
  22. 22.790 + 99 =
  23. 23.32 + 9 =
  24. 24.47 + 9 =
  25. 25.841 − 99 =
  26. 26.70 − 29 =
  27. 27.306 + 99 =
  28. 28.58 + 9 =
  29. 29.27 + 9 =
  30. 30.53 + 19 =
  31. 31.13 + 29 =
  32. 32.46 − 29 =
  33. 33.43 + 19 =
  34. 34.54 + 29 =
  35. 35.77 + 29 =
  36. 36.84 − 19 =
  37. 37.20 + 29 =
  38. 38.15 + 29 =
  39. 39.59 − 19 =
  40. 40.61 + 29 =

Answer key

  1. 583
  2. 96
  3. 71
  4. 39
  5. 64
  6. 21
  7. 35
  8. 542
  9. 65
  10. 628
  11. 515
  12. 55
  13. 42
  14. 68
  15. 11
  16. 94
  17. 20
  18. 799
  19. 51
  20. 74
  21. 69
  22. 889
  23. 41
  24. 56
  25. 742
  26. 41
  27. 405
  28. 67
  29. 36
  30. 72
  31. 42
  32. 17
  33. 62
  34. 83
  35. 106
  36. 65
  37. 49
  38. 44
  39. 40
  40. 90

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