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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 118 · 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. 1.54 − 29 =
  2. 2.20 + 29 =
  3. 3.56 + 29 =
  4. 4.87 − 9 =
  5. 5.79 + 9 =
  6. 6.37 + 29 =
  7. 7.74 + 9 =
  8. 8.29 − 19 =
  9. 9.387 + 99 =
  10. 10.25 + 29 =
  11. 11.22 − 19 =
  12. 12.306 − 99 =
  13. 13.34 − 19 =
  14. 14.504 + 99 =
  15. 15.32 + 19 =
  16. 16.80 − 19 =
  17. 17.21 + 29 =
  18. 18.445 + 99 =
  19. 19.653 − 99 =
  20. 20.19 + 9 =
  21. 21.18 − 9 =
  22. 22.158 + 99 =
  23. 23.74 − 9 =
  24. 24.646 − 99 =
  25. 25.70 − 29 =
  26. 26.311 + 99 =
  27. 27.39 − 9 =
  28. 28.55 + 9 =
  29. 29.67 + 29 =
  30. 30.16 + 19 =
  31. 31.44 − 29 =
  32. 32.28 − 19 =
  33. 33.86 − 29 =
  34. 34.33 − 29 =
  35. 35.34 + 19 =
  36. 36.60 + 29 =
  37. 37.68 + 19 =
  38. 38.58 − 29 =
  39. 39.159 − 99 =
  40. 40.67 + 9 =

Answer key

  1. 25
  2. 49
  3. 85
  4. 78
  5. 88
  6. 66
  7. 83
  8. 10
  9. 486
  10. 54
  11. 3
  12. 207
  13. 15
  14. 603
  15. 51
  16. 61
  17. 50
  18. 544
  19. 554
  20. 28
  21. 9
  22. 257
  23. 65
  24. 547
  25. 41
  26. 410
  27. 30
  28. 64
  29. 96
  30. 35
  31. 15
  32. 9
  33. 57
  34. 4
  35. 53
  36. 89
  37. 87
  38. 29
  39. 60
  40. 76

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