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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 272 · 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. 1.23 + 29 =
  2. 2.74 − 9 =
  3. 3.76 + 19 =
  4. 4.14 − 9 =
  5. 5.339 − 99 =
  6. 6.31 + 19 =
  7. 7.75 + 9 =
  8. 8.638 + 99 =
  9. 9.52 − 19 =
  10. 10.19 + 19 =
  11. 11.46 − 29 =
  12. 12.83 − 9 =
  13. 13.141 + 99 =
  14. 14.35 + 29 =
  15. 15.750 + 99 =
  16. 16.35 − 19 =
  17. 17.33 + 19 =
  18. 18.48 + 29 =
  19. 19.118 + 99 =
  20. 20.89 − 9 =
  21. 21.508 + 99 =
  22. 22.88 − 19 =
  23. 23.48 − 19 =
  24. 24.36 + 29 =
  25. 25.39 − 29 =
  26. 26.568 + 99 =
  27. 27.38 − 29 =
  28. 28.95 − 29 =
  29. 29.27 + 29 =
  30. 30.37 + 9 =
  31. 31.22 + 19 =
  32. 32.24 + 9 =
  33. 33.44 + 19 =
  34. 34.37 + 19 =
  35. 35.289 + 99 =
  36. 36.32 + 9 =
  37. 37.52 + 9 =
  38. 38.299 − 99 =
  39. 39.70 + 9 =
  40. 40.39 − 9 =

Answer key

  1. 52
  2. 65
  3. 95
  4. 5
  5. 240
  6. 50
  7. 84
  8. 737
  9. 33
  10. 38
  11. 17
  12. 74
  13. 240
  14. 64
  15. 849
  16. 16
  17. 52
  18. 77
  19. 217
  20. 80
  21. 607
  22. 69
  23. 29
  24. 65
  25. 10
  26. 667
  27. 9
  28. 66
  29. 56
  30. 46
  31. 41
  32. 33
  33. 63
  34. 56
  35. 388
  36. 41
  37. 61
  38. 200
  39. 79
  40. 30

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