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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 712 · 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. 1.348 + 99 =
  2. 2.79 − 29 =
  3. 3.95 − 19 =
  4. 4.23 − 19 =
  5. 5.40 + 19 =
  6. 6.59 − 19 =
  7. 7.68 + 9 =
  8. 8.62 + 19 =
  9. 9.396 − 99 =
  10. 10.43 + 19 =
  11. 11.91 − 29 =
  12. 12.59 + 29 =
  13. 13.58 + 29 =
  14. 14.60 + 19 =
  15. 15.60 + 9 =
  16. 16.53 + 19 =
  17. 17.60 + 29 =
  18. 18.37 + 19 =
  19. 19.309 − 99 =
  20. 20.589 + 99 =
  21. 21.97 − 19 =
  22. 22.65 + 19 =
  23. 23.64 + 9 =
  24. 24.42 + 9 =
  25. 25.27 − 19 =
  26. 26.222 − 99 =
  27. 27.23 + 19 =
  28. 28.87 − 19 =
  29. 29.77 − 19 =
  30. 30.37 − 29 =
  31. 31.47 + 19 =
  32. 32.66 + 29 =
  33. 33.17 + 29 =
  34. 34.30 − 19 =
  35. 35.549 + 99 =
  36. 36.70 + 9 =
  37. 37.27 + 19 =
  38. 38.63 + 19 =
  39. 39.883 − 99 =
  40. 40.737 + 99 =

Answer key

  1. 447
  2. 50
  3. 76
  4. 4
  5. 59
  6. 40
  7. 77
  8. 81
  9. 297
  10. 62
  11. 62
  12. 88
  13. 87
  14. 79
  15. 69
  16. 72
  17. 89
  18. 56
  19. 210
  20. 688
  21. 78
  22. 84
  23. 73
  24. 51
  25. 8
  26. 123
  27. 42
  28. 68
  29. 58
  30. 8
  31. 66
  32. 95
  33. 46
  34. 11
  35. 648
  36. 79
  37. 46
  38. 82
  39. 784
  40. 836

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