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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 488 · 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. 1.85 − 9 =
  2. 2.80 − 29 =
  3. 3.34 − 9 =
  4. 4.81 − 29 =
  5. 5.59 − 29 =
  6. 6.30 + 9 =
  7. 7.55 + 29 =
  8. 8.39 + 19 =
  9. 9.25 + 19 =
  10. 10.50 − 29 =
  11. 11.30 + 19 =
  12. 12.231 − 99 =
  13. 13.19 + 29 =
  14. 14.46 − 29 =
  15. 15.109 − 29 =
  16. 16.104 − 29 =
  17. 17.34 − 19 =
  18. 18.37 − 9 =
  19. 19.75 + 29 =
  20. 20.309 − 99 =
  21. 21.13 + 19 =
  22. 22.726 + 99 =
  23. 23.66 − 9 =
  24. 24.274 − 99 =
  25. 25.59 + 29 =
  26. 26.235 + 99 =
  27. 27.52 + 19 =
  28. 28.33 − 19 =
  29. 29.66 − 29 =
  30. 30.21 + 9 =
  31. 31.80 − 9 =
  32. 32.17 + 9 =
  33. 33.78 − 19 =
  34. 34.256 − 99 =
  35. 35.57 − 9 =
  36. 36.43 + 9 =
  37. 37.427 − 99 =
  38. 38.560 − 99 =
  39. 39.69 + 9 =
  40. 40.37 + 9 =

Answer key

  1. 76
  2. 51
  3. 25
  4. 52
  5. 30
  6. 39
  7. 84
  8. 58
  9. 44
  10. 21
  11. 49
  12. 132
  13. 48
  14. 17
  15. 80
  16. 75
  17. 15
  18. 28
  19. 104
  20. 210
  21. 32
  22. 825
  23. 57
  24. 175
  25. 88
  26. 334
  27. 71
  28. 14
  29. 37
  30. 30
  31. 71
  32. 26
  33. 59
  34. 157
  35. 48
  36. 52
  37. 328
  38. 461
  39. 78
  40. 46

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