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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 216 · 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. 1.57 + 29 =
  2. 2.429 − 99 =
  3. 3.42 + 9 =
  4. 4.750 + 99 =
  5. 5.90 − 29 =
  6. 6.88 − 19 =
  7. 7.58 + 19 =
  8. 8.83 − 9 =
  9. 9.73 − 9 =
  10. 10.239 + 99 =
  11. 11.640 + 99 =
  12. 12.109 − 29 =
  13. 13.50 + 29 =
  14. 14.45 + 19 =
  15. 15.35 + 9 =
  16. 16.26 + 9 =
  17. 17.502 − 99 =
  18. 18.33 + 19 =
  19. 19.44 − 19 =
  20. 20.207 − 99 =
  21. 21.41 − 19 =
  22. 22.36 + 9 =
  23. 23.131 + 99 =
  24. 24.38 − 9 =
  25. 25.63 + 19 =
  26. 26.39 + 19 =
  27. 27.89 − 19 =
  28. 28.52 + 9 =
  29. 29.168 − 99 =
  30. 30.786 − 99 =
  31. 31.57 + 19 =
  32. 32.42 + 29 =
  33. 33.26 + 19 =
  34. 34.20 + 19 =
  35. 35.51 + 19 =
  36. 36.56 + 29 =
  37. 37.31 + 9 =
  38. 38.180 − 99 =
  39. 39.840 − 99 =
  40. 40.27 + 29 =

Answer key

  1. 86
  2. 330
  3. 51
  4. 849
  5. 61
  6. 69
  7. 77
  8. 74
  9. 64
  10. 338
  11. 739
  12. 80
  13. 79
  14. 64
  15. 44
  16. 35
  17. 403
  18. 52
  19. 25
  20. 108
  21. 22
  22. 45
  23. 230
  24. 29
  25. 82
  26. 58
  27. 70
  28. 61
  29. 69
  30. 687
  31. 76
  32. 71
  33. 45
  34. 39
  35. 70
  36. 85
  37. 40
  38. 81
  39. 741
  40. 56

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