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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 339 · 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. 1.64 + 9 =
  2. 2.161 + 99 =
  3. 3.62 + 9 =
  4. 4.82 − 19 =
  5. 5.66 − 29 =
  6. 6.37 + 9 =
  7. 7.42 + 9 =
  8. 8.81 − 19 =
  9. 9.34 + 9 =
  10. 10.16 + 9 =
  11. 11.340 − 99 =
  12. 12.852 − 99 =
  13. 13.51 − 9 =
  14. 14.297 + 99 =
  15. 15.12 + 9 =
  16. 16.33 − 19 =
  17. 17.84 − 29 =
  18. 18.77 − 19 =
  19. 19.53 + 19 =
  20. 20.32 + 9 =
  21. 21.399 − 99 =
  22. 22.83 − 29 =
  23. 23.888 − 99 =
  24. 24.36 + 19 =
  25. 25.77 + 19 =
  26. 26.27 + 29 =
  27. 27.26 − 9 =
  28. 28.73 + 9 =
  29. 29.39 − 19 =
  30. 30.57 − 9 =
  31. 31.649 + 99 =
  32. 32.291 + 99 =
  33. 33.32 − 29 =
  34. 34.31 + 9 =
  35. 35.585 + 99 =
  36. 36.71 + 19 =
  37. 37.527 − 99 =
  38. 38.662 − 99 =
  39. 39.69 − 29 =
  40. 40.357 − 99 =

Answer key

  1. 73
  2. 260
  3. 71
  4. 63
  5. 37
  6. 46
  7. 51
  8. 62
  9. 43
  10. 25
  11. 241
  12. 753
  13. 42
  14. 396
  15. 21
  16. 14
  17. 55
  18. 58
  19. 72
  20. 41
  21. 300
  22. 54
  23. 789
  24. 55
  25. 96
  26. 56
  27. 17
  28. 82
  29. 20
  30. 48
  31. 748
  32. 390
  33. 3
  34. 40
  35. 684
  36. 90
  37. 428
  38. 563
  39. 40
  40. 258

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