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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 362 · 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. 1.16 − 9 =
  2. 2.106 − 29 =
  3. 3.320 − 99 =
  4. 4.30 + 9 =
  5. 5.26 + 19 =
  6. 6.829 − 99 =
  7. 7.863 − 99 =
  8. 8.21 − 9 =
  9. 9.22 + 9 =
  10. 10.687 − 99 =
  11. 11.42 − 29 =
  12. 12.60 − 9 =
  13. 13.272 + 99 =
  14. 14.333 − 99 =
  15. 15.749 + 99 =
  16. 16.69 − 29 =
  17. 17.77 − 9 =
  18. 18.558 − 99 =
  19. 19.123 + 99 =
  20. 20.740 − 99 =
  21. 21.84 − 19 =
  22. 22.297 − 99 =
  23. 23.33 + 29 =
  24. 24.14 + 19 =
  25. 25.55 + 9 =
  26. 26.22 + 19 =
  27. 27.82 − 19 =
  28. 28.95 − 19 =
  29. 29.12 + 9 =
  30. 30.89 − 19 =
  31. 31.43 − 9 =
  32. 32.66 + 9 =
  33. 33.49 + 29 =
  34. 34.441 + 99 =
  35. 35.38 + 19 =
  36. 36.36 + 29 =
  37. 37.21 + 9 =
  38. 38.809 − 99 =
  39. 39.79 + 9 =
  40. 40.49 + 9 =

Answer key

  1. 7
  2. 77
  3. 221
  4. 39
  5. 45
  6. 730
  7. 764
  8. 12
  9. 31
  10. 588
  11. 13
  12. 51
  13. 371
  14. 234
  15. 848
  16. 40
  17. 68
  18. 459
  19. 222
  20. 641
  21. 65
  22. 198
  23. 62
  24. 33
  25. 64
  26. 41
  27. 63
  28. 76
  29. 21
  30. 70
  31. 34
  32. 75
  33. 78
  34. 540
  35. 57
  36. 65
  37. 30
  38. 710
  39. 88
  40. 58

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