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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 133 · 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. 1.52 + 9 =
  2. 2.21 − 9 =
  3. 3.71 − 9 =
  4. 4.76 + 29 =
  5. 5.25 + 9 =
  6. 6.692 + 99 =
  7. 7.39 + 29 =
  8. 8.56 − 9 =
  9. 9.57 + 19 =
  10. 10.19 − 9 =
  11. 11.99 − 29 =
  12. 12.96 − 29 =
  13. 13.66 − 19 =
  14. 14.74 + 9 =
  15. 15.46 + 19 =
  16. 16.20 − 9 =
  17. 17.445 − 99 =
  18. 18.44 + 9 =
  19. 19.75 − 9 =
  20. 20.60 + 19 =
  21. 21.72 + 29 =
  22. 22.677 − 99 =
  23. 23.53 + 29 =
  24. 24.18 + 19 =
  25. 25.35 + 9 =
  26. 26.35 − 19 =
  27. 27.215 + 99 =
  28. 28.76 − 9 =
  29. 29.94 − 29 =
  30. 30.39 + 19 =
  31. 31.57 + 29 =
  32. 32.20 + 9 =
  33. 33.297 − 99 =
  34. 34.252 − 99 =
  35. 35.78 − 9 =
  36. 36.732 + 99 =
  37. 37.533 + 99 =
  38. 38.17 + 19 =
  39. 39.750 − 99 =
  40. 40.69 + 9 =

Answer key

  1. 61
  2. 12
  3. 62
  4. 105
  5. 34
  6. 791
  7. 68
  8. 47
  9. 76
  10. 10
  11. 70
  12. 67
  13. 47
  14. 83
  15. 65
  16. 11
  17. 346
  18. 53
  19. 66
  20. 79
  21. 101
  22. 578
  23. 82
  24. 37
  25. 44
  26. 16
  27. 314
  28. 67
  29. 65
  30. 58
  31. 86
  32. 29
  33. 198
  34. 153
  35. 69
  36. 831
  37. 632
  38. 36
  39. 651
  40. 78

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