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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 4 · 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. 1.383 + 99 =
  2. 2.341 + 99 =
  3. 3.22 − 19 =
  4. 4.79 − 19 =
  5. 5.39 + 29 =
  6. 6.185 − 99 =
  7. 7.63 + 9 =
  8. 8.47 − 9 =
  9. 9.45 + 19 =
  10. 10.74 + 9 =
  11. 11.522 + 99 =
  12. 12.46 − 9 =
  13. 13.64 − 19 =
  14. 14.73 − 19 =
  15. 15.57 − 19 =
  16. 16.63 + 29 =
  17. 17.60 + 29 =
  18. 18.42 − 9 =
  19. 19.35 − 19 =
  20. 20.64 − 9 =
  21. 21.44 − 19 =
  22. 22.94 − 19 =
  23. 23.38 + 9 =
  24. 24.815 − 99 =
  25. 25.38 − 29 =
  26. 26.71 + 9 =
  27. 27.477 − 99 =
  28. 28.69 − 9 =
  29. 29.680 + 99 =
  30. 30.615 + 99 =
  31. 31.363 − 99 =
  32. 32.118 + 99 =
  33. 33.55 + 9 =
  34. 34.47 + 19 =
  35. 35.15 + 29 =
  36. 36.49 + 19 =
  37. 37.531 + 99 =
  38. 38.78 + 29 =
  39. 39.316 + 99 =
  40. 40.76 + 9 =

Answer key

  1. 482
  2. 440
  3. 3
  4. 60
  5. 68
  6. 86
  7. 72
  8. 38
  9. 64
  10. 83
  11. 621
  12. 37
  13. 45
  14. 54
  15. 38
  16. 92
  17. 89
  18. 33
  19. 16
  20. 55
  21. 25
  22. 75
  23. 47
  24. 716
  25. 9
  26. 80
  27. 378
  28. 60
  29. 779
  30. 714
  31. 264
  32. 217
  33. 64
  34. 66
  35. 44
  36. 68
  37. 630
  38. 107
  39. 415
  40. 85

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