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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 304 · 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. 1.594 − 99 =
  2. 2.667 + 99 =
  3. 3.81 − 19 =
  4. 4.726 + 99 =
  5. 5.35 + 29 =
  6. 6.46 − 19 =
  7. 7.32 − 9 =
  8. 8.45 + 9 =
  9. 9.36 + 19 =
  10. 10.34 − 9 =
  11. 11.31 − 9 =
  12. 12.587 + 99 =
  13. 13.739 − 99 =
  14. 14.309 − 99 =
  15. 15.63 + 29 =
  16. 16.40 − 29 =
  17. 17.22 + 29 =
  18. 18.791 + 99 =
  19. 19.98 − 29 =
  20. 20.91 − 29 =
  21. 21.27 + 19 =
  22. 22.51 + 19 =
  23. 23.95 − 19 =
  24. 24.45 − 29 =
  25. 25.23 + 9 =
  26. 26.585 − 99 =
  27. 27.35 + 9 =
  28. 28.453 − 99 =
  29. 29.685 + 99 =
  30. 30.749 − 99 =
  31. 31.40 − 19 =
  32. 32.88 − 19 =
  33. 33.65 − 9 =
  34. 34.42 + 19 =
  35. 35.77 + 29 =
  36. 36.71 + 19 =
  37. 37.99 − 29 =
  38. 38.57 + 19 =
  39. 39.47 + 19 =
  40. 40.761 − 99 =

Answer key

  1. 495
  2. 766
  3. 62
  4. 825
  5. 64
  6. 27
  7. 23
  8. 54
  9. 55
  10. 25
  11. 22
  12. 686
  13. 640
  14. 210
  15. 92
  16. 11
  17. 51
  18. 890
  19. 69
  20. 62
  21. 46
  22. 70
  23. 76
  24. 16
  25. 32
  26. 486
  27. 44
  28. 354
  29. 784
  30. 650
  31. 21
  32. 69
  33. 56
  34. 61
  35. 106
  36. 90
  37. 70
  38. 76
  39. 66
  40. 662

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