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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 161 · 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. 1.692 + 99 =
  2. 2.61 + 19 =
  3. 3.48 − 19 =
  4. 4.638 + 99 =
  5. 5.864 − 99 =
  6. 6.83 − 29 =
  7. 7.33 − 19 =
  8. 8.61 − 29 =
  9. 9.36 + 19 =
  10. 10.579 + 99 =
  11. 11.56 + 19 =
  12. 12.211 − 99 =
  13. 13.54 + 19 =
  14. 14.46 − 9 =
  15. 15.530 + 99 =
  16. 16.36 − 29 =
  17. 17.70 + 9 =
  18. 18.725 − 99 =
  19. 19.79 + 29 =
  20. 20.16 + 19 =
  21. 21.60 − 29 =
  22. 22.52 + 29 =
  23. 23.24 − 19 =
  24. 24.62 − 19 =
  25. 25.17 + 19 =
  26. 26.44 + 19 =
  27. 27.24 − 9 =
  28. 28.46 + 19 =
  29. 29.40 + 19 =
  30. 30.678 − 99 =
  31. 31.20 + 9 =
  32. 32.77 + 29 =
  33. 33.39 + 29 =
  34. 34.52 − 29 =
  35. 35.41 + 19 =
  36. 36.442 − 99 =
  37. 37.45 + 19 =
  38. 38.81 − 19 =
  39. 39.98 − 29 =
  40. 40.64 + 19 =

Answer key

  1. 791
  2. 80
  3. 29
  4. 737
  5. 765
  6. 54
  7. 14
  8. 32
  9. 55
  10. 678
  11. 75
  12. 112
  13. 73
  14. 37
  15. 629
  16. 7
  17. 79
  18. 626
  19. 108
  20. 35
  21. 31
  22. 81
  23. 5
  24. 43
  25. 36
  26. 63
  27. 15
  28. 65
  29. 59
  30. 579
  31. 29
  32. 106
  33. 68
  34. 23
  35. 60
  36. 343
  37. 64
  38. 62
  39. 69
  40. 83

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