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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 179 · 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. 1.546 − 99 =
  2. 2.31 + 29 =
  3. 3.48 − 19 =
  4. 4.42 − 9 =
  5. 5.84 − 9 =
  6. 6.66 − 9 =
  7. 7.35 − 29 =
  8. 8.68 − 19 =
  9. 9.518 − 99 =
  10. 10.56 + 29 =
  11. 11.47 + 29 =
  12. 12.77 + 19 =
  13. 13.53 + 29 =
  14. 14.63 + 29 =
  15. 15.58 + 29 =
  16. 16.503 − 99 =
  17. 17.95 − 19 =
  18. 18.90 − 29 =
  19. 19.64 + 19 =
  20. 20.26 + 9 =
  21. 21.41 − 29 =
  22. 22.59 − 19 =
  23. 23.798 + 99 =
  24. 24.154 − 99 =
  25. 25.35 + 29 =
  26. 26.47 + 9 =
  27. 27.45 − 9 =
  28. 28.400 + 99 =
  29. 29.41 − 9 =
  30. 30.17 + 29 =
  31. 31.40 − 9 =
  32. 32.52 − 9 =
  33. 33.294 + 99 =
  34. 34.46 + 19 =
  35. 35.28 − 19 =
  36. 36.689 − 99 =
  37. 37.60 + 9 =
  38. 38.27 + 19 =
  39. 39.73 + 9 =
  40. 40.418 + 99 =

Answer key

  1. 447
  2. 60
  3. 29
  4. 33
  5. 75
  6. 57
  7. 6
  8. 49
  9. 419
  10. 85
  11. 76
  12. 96
  13. 82
  14. 92
  15. 87
  16. 404
  17. 76
  18. 61
  19. 83
  20. 35
  21. 12
  22. 40
  23. 897
  24. 55
  25. 64
  26. 56
  27. 36
  28. 499
  29. 32
  30. 46
  31. 31
  32. 43
  33. 393
  34. 65
  35. 9
  36. 590
  37. 69
  38. 46
  39. 82
  40. 517

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