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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 485 · 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. 1.645 − 99 =
  2. 2.715 + 99 =
  3. 3.81 − 19 =
  4. 4.98 − 19 =
  5. 5.62 + 9 =
  6. 6.482 − 99 =
  7. 7.46 + 9 =
  8. 8.98 − 29 =
  9. 9.77 − 19 =
  10. 10.41 − 19 =
  11. 11.24 − 19 =
  12. 12.89 − 19 =
  13. 13.75 + 19 =
  14. 14.76 + 9 =
  15. 15.22 + 9 =
  16. 16.70 − 19 =
  17. 17.77 + 19 =
  18. 18.67 + 19 =
  19. 19.75 − 19 =
  20. 20.46 − 19 =
  21. 21.189 − 99 =
  22. 22.26 + 9 =
  23. 23.21 + 19 =
  24. 24.50 − 9 =
  25. 25.66 + 9 =
  26. 26.40 + 9 =
  27. 27.22 − 19 =
  28. 28.73 + 19 =
  29. 29.50 + 19 =
  30. 30.576 + 99 =
  31. 31.49 − 9 =
  32. 32.226 − 99 =
  33. 33.785 + 99 =
  34. 34.12 − 9 =
  35. 35.57 + 19 =
  36. 36.365 − 99 =
  37. 37.339 + 99 =
  38. 38.55 + 9 =
  39. 39.102 − 29 =
  40. 40.22 + 19 =

Answer key

  1. 546
  2. 814
  3. 62
  4. 79
  5. 71
  6. 383
  7. 55
  8. 69
  9. 58
  10. 22
  11. 5
  12. 70
  13. 94
  14. 85
  15. 31
  16. 51
  17. 96
  18. 86
  19. 56
  20. 27
  21. 90
  22. 35
  23. 40
  24. 41
  25. 75
  26. 49
  27. 3
  28. 92
  29. 69
  30. 675
  31. 40
  32. 127
  33. 884
  34. 3
  35. 76
  36. 266
  37. 438
  38. 64
  39. 73
  40. 41

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