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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 823 · 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. 1.147 + 99 =
  2. 2.51 + 9 =
  3. 3.88 − 29 =
  4. 4.77 − 9 =
  5. 5.69 + 9 =
  6. 6.35 + 9 =
  7. 7.33 + 19 =
  8. 8.58 − 19 =
  9. 9.48 + 19 =
  10. 10.73 + 29 =
  11. 11.56 − 19 =
  12. 12.39 − 9 =
  13. 13.533 − 99 =
  14. 14.24 + 29 =
  15. 15.57 + 19 =
  16. 16.77 + 29 =
  17. 17.650 − 99 =
  18. 18.65 + 29 =
  19. 19.42 − 9 =
  20. 20.46 + 9 =
  21. 21.58 + 9 =
  22. 22.61 + 29 =
  23. 23.101 − 29 =
  24. 24.81 − 19 =
  25. 25.66 + 9 =
  26. 26.304 + 99 =
  27. 27.74 + 19 =
  28. 28.27 + 9 =
  29. 29.86 − 29 =
  30. 30.872 − 99 =
  31. 31.77 + 19 =
  32. 32.15 + 19 =
  33. 33.823 − 99 =
  34. 34.547 + 99 =
  35. 35.48 − 9 =
  36. 36.47 + 19 =
  37. 37.22 − 9 =
  38. 38.39 − 19 =
  39. 39.795 − 99 =
  40. 40.51 − 9 =

Answer key

  1. 246
  2. 60
  3. 59
  4. 68
  5. 78
  6. 44
  7. 52
  8. 39
  9. 67
  10. 102
  11. 37
  12. 30
  13. 434
  14. 53
  15. 76
  16. 106
  17. 551
  18. 94
  19. 33
  20. 55
  21. 67
  22. 90
  23. 72
  24. 62
  25. 75
  26. 403
  27. 93
  28. 36
  29. 57
  30. 773
  31. 96
  32. 34
  33. 724
  34. 646
  35. 39
  36. 66
  37. 13
  38. 20
  39. 696
  40. 42

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