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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 211 · 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. 1.84 − 19 =
  2. 2.62 + 29 =
  3. 3.96 − 19 =
  4. 4.53 − 29 =
  5. 5.50 + 29 =
  6. 6.13 − 9 =
  7. 7.31 − 9 =
  8. 8.54 + 9 =
  9. 9.715 + 99 =
  10. 10.72 + 19 =
  11. 11.62 − 29 =
  12. 12.663 − 99 =
  13. 13.63 + 29 =
  14. 14.70 − 9 =
  15. 15.65 − 9 =
  16. 16.55 − 19 =
  17. 17.64 + 19 =
  18. 18.49 + 9 =
  19. 19.42 + 9 =
  20. 20.20 + 29 =
  21. 21.261 + 99 =
  22. 22.63 + 9 =
  23. 23.46 + 29 =
  24. 24.78 + 29 =
  25. 25.98 − 19 =
  26. 26.80 + 29 =
  27. 27.417 − 99 =
  28. 28.62 − 19 =
  29. 29.20 − 9 =
  30. 30.174 − 99 =
  31. 31.46 + 19 =
  32. 32.29 − 9 =
  33. 33.33 + 29 =
  34. 34.179 + 99 =
  35. 35.71 + 29 =
  36. 36.33 − 29 =
  37. 37.48 − 19 =
  38. 38.57 + 19 =
  39. 39.413 + 99 =
  40. 40.39 + 19 =

Answer key

  1. 65
  2. 91
  3. 77
  4. 24
  5. 79
  6. 4
  7. 22
  8. 63
  9. 814
  10. 91
  11. 33
  12. 564
  13. 92
  14. 61
  15. 56
  16. 36
  17. 83
  18. 58
  19. 51
  20. 49
  21. 360
  22. 72
  23. 75
  24. 107
  25. 79
  26. 109
  27. 318
  28. 43
  29. 11
  30. 75
  31. 65
  32. 20
  33. 62
  34. 278
  35. 100
  36. 4
  37. 29
  38. 76
  39. 512
  40. 58

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