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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 856 · 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. 1.37 + 9 =
  2. 2.64 + 29 =
  3. 3.464 + 99 =
  4. 4.27 + 29 =
  5. 5.752 + 99 =
  6. 6.70 + 29 =
  7. 7.66 + 19 =
  8. 8.202 − 99 =
  9. 9.88 − 19 =
  10. 10.50 − 29 =
  11. 11.75 − 19 =
  12. 12.39 − 29 =
  13. 13.28 + 29 =
  14. 14.699 + 99 =
  15. 15.138 + 99 =
  16. 16.17 + 19 =
  17. 17.42 − 29 =
  18. 18.302 − 99 =
  19. 19.63 + 19 =
  20. 20.291 − 99 =
  21. 21.433 + 99 =
  22. 22.130 + 99 =
  23. 23.301 − 99 =
  24. 24.61 − 19 =
  25. 25.20 + 19 =
  26. 26.14 + 19 =
  27. 27.74 − 9 =
  28. 28.31 + 9 =
  29. 29.17 − 9 =
  30. 30.32 + 9 =
  31. 31.50 − 9 =
  32. 32.680 + 99 =
  33. 33.69 + 19 =
  34. 34.49 − 9 =
  35. 35.663 + 99 =
  36. 36.94 − 29 =
  37. 37.78 + 9 =
  38. 38.89 − 9 =
  39. 39.60 − 9 =
  40. 40.63 + 9 =

Answer key

  1. 46
  2. 93
  3. 563
  4. 56
  5. 851
  6. 99
  7. 85
  8. 103
  9. 69
  10. 21
  11. 56
  12. 10
  13. 57
  14. 798
  15. 237
  16. 36
  17. 13
  18. 203
  19. 82
  20. 192
  21. 532
  22. 229
  23. 202
  24. 42
  25. 39
  26. 33
  27. 65
  28. 40
  29. 8
  30. 41
  31. 41
  32. 779
  33. 88
  34. 40
  35. 762
  36. 65
  37. 87
  38. 80
  39. 51
  40. 72

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