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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 151 · 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. 1.626 − 99 =
  2. 2.632 + 99 =
  3. 3.659 + 99 =
  4. 4.42 + 19 =
  5. 5.16 − 9 =
  6. 6.73 + 19 =
  7. 7.29 − 9 =
  8. 8.42 − 29 =
  9. 9.68 + 9 =
  10. 10.88 − 9 =
  11. 11.205 − 99 =
  12. 12.22 − 19 =
  13. 13.23 + 29 =
  14. 14.357 − 99 =
  15. 15.37 + 19 =
  16. 16.48 − 9 =
  17. 17.584 + 99 =
  18. 18.27 − 19 =
  19. 19.43 − 29 =
  20. 20.36 − 9 =
  21. 21.638 + 99 =
  22. 22.104 − 29 =
  23. 23.26 + 29 =
  24. 24.59 + 19 =
  25. 25.74 − 29 =
  26. 26.84 − 9 =
  27. 27.753 + 99 =
  28. 28.713 − 99 =
  29. 29.61 + 19 =
  30. 30.687 + 99 =
  31. 31.93 − 19 =
  32. 32.56 + 9 =
  33. 33.85 − 29 =
  34. 34.515 − 99 =
  35. 35.65 + 9 =
  36. 36.74 + 9 =
  37. 37.316 + 99 =
  38. 38.64 − 9 =
  39. 39.25 − 19 =
  40. 40.37 − 9 =

Answer key

  1. 527
  2. 731
  3. 758
  4. 61
  5. 7
  6. 92
  7. 20
  8. 13
  9. 77
  10. 79
  11. 106
  12. 3
  13. 52
  14. 258
  15. 56
  16. 39
  17. 683
  18. 8
  19. 14
  20. 27
  21. 737
  22. 75
  23. 55
  24. 78
  25. 45
  26. 75
  27. 852
  28. 614
  29. 80
  30. 786
  31. 74
  32. 65
  33. 56
  34. 416
  35. 74
  36. 83
  37. 415
  38. 55
  39. 6
  40. 28

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