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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 875 · 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. 1.67 − 29 =
  2. 2.293 + 99 =
  3. 3.33 − 19 =
  4. 4.80 + 29 =
  5. 5.28 + 19 =
  6. 6.94 − 19 =
  7. 7.368 − 99 =
  8. 8.89 − 9 =
  9. 9.61 + 9 =
  10. 10.60 − 29 =
  11. 11.21 + 9 =
  12. 12.83 − 29 =
  13. 13.71 − 9 =
  14. 14.79 − 19 =
  15. 15.69 + 29 =
  16. 16.94 − 29 =
  17. 17.134 + 99 =
  18. 18.211 + 99 =
  19. 19.793 + 99 =
  20. 20.66 + 29 =
  21. 21.24 + 9 =
  22. 22.19 + 19 =
  23. 23.53 − 9 =
  24. 24.61 − 29 =
  25. 25.37 − 9 =
  26. 26.61 − 19 =
  27. 27.352 − 99 =
  28. 28.19 + 9 =
  29. 29.71 + 29 =
  30. 30.439 + 99 =
  31. 31.241 − 99 =
  32. 32.46 − 29 =
  33. 33.87 − 29 =
  34. 34.32 + 19 =
  35. 35.357 − 99 =
  36. 36.78 − 29 =
  37. 37.15 + 19 =
  38. 38.38 − 9 =
  39. 39.46 + 9 =
  40. 40.76 + 9 =

Answer key

  1. 38
  2. 392
  3. 14
  4. 109
  5. 47
  6. 75
  7. 269
  8. 80
  9. 70
  10. 31
  11. 30
  12. 54
  13. 62
  14. 60
  15. 98
  16. 65
  17. 233
  18. 310
  19. 892
  20. 95
  21. 33
  22. 38
  23. 44
  24. 32
  25. 28
  26. 42
  27. 253
  28. 28
  29. 100
  30. 538
  31. 142
  32. 17
  33. 58
  34. 51
  35. 258
  36. 49
  37. 34
  38. 29
  39. 55
  40. 85

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