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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 972 · 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. 1.37 − 9 =
  2. 2.23 + 29 =
  3. 3.22 + 19 =
  4. 4.58 + 19 =
  5. 5.54 + 29 =
  6. 6.52 + 19 =
  7. 7.98 − 29 =
  8. 8.82 − 9 =
  9. 9.70 + 9 =
  10. 10.13 + 29 =
  11. 11.28 − 19 =
  12. 12.181 − 99 =
  13. 13.254 − 99 =
  14. 14.259 + 99 =
  15. 15.56 − 19 =
  16. 16.747 + 99 =
  17. 17.270 + 99 =
  18. 18.52 − 9 =
  19. 19.41 − 29 =
  20. 20.37 + 29 =
  21. 21.78 + 9 =
  22. 22.25 − 9 =
  23. 23.77 + 19 =
  24. 24.161 − 99 =
  25. 25.92 − 29 =
  26. 26.85 − 19 =
  27. 27.43 − 9 =
  28. 28.51 + 19 =
  29. 29.22 + 9 =
  30. 30.507 − 99 =
  31. 31.63 − 19 =
  32. 32.15 + 29 =
  33. 33.786 − 99 =
  34. 34.35 − 9 =
  35. 35.71 − 9 =
  36. 36.58 − 9 =
  37. 37.44 − 9 =
  38. 38.65 + 29 =
  39. 39.66 − 9 =
  40. 40.84 − 9 =

Answer key

  1. 28
  2. 52
  3. 41
  4. 77
  5. 83
  6. 71
  7. 69
  8. 73
  9. 79
  10. 42
  11. 9
  12. 82
  13. 155
  14. 358
  15. 37
  16. 846
  17. 369
  18. 43
  19. 12
  20. 66
  21. 87
  22. 16
  23. 96
  24. 62
  25. 63
  26. 66
  27. 34
  28. 70
  29. 31
  30. 408
  31. 44
  32. 44
  33. 687
  34. 26
  35. 62
  36. 49
  37. 35
  38. 94
  39. 57
  40. 75

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