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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 444 · 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. 1.84 − 29 =
  2. 2.21 + 9 =
  3. 3.507 − 99 =
  4. 4.60 + 9 =
  5. 5.173 + 99 =
  6. 6.293 − 99 =
  7. 7.54 + 29 =
  8. 8.74 + 9 =
  9. 9.37 − 19 =
  10. 10.72 − 19 =
  11. 11.81 − 29 =
  12. 12.78 + 19 =
  13. 13.86 − 29 =
  14. 14.71 − 29 =
  15. 15.68 + 29 =
  16. 16.71 + 29 =
  17. 17.94 − 19 =
  18. 18.44 − 19 =
  19. 19.12 + 19 =
  20. 20.730 + 99 =
  21. 21.51 − 9 =
  22. 22.49 − 19 =
  23. 23.73 − 29 =
  24. 24.38 + 29 =
  25. 25.116 + 99 =
  26. 26.590 − 99 =
  27. 27.209 + 99 =
  28. 28.283 + 99 =
  29. 29.22 + 9 =
  30. 30.474 + 99 =
  31. 31.55 − 9 =
  32. 32.42 + 29 =
  33. 33.39 − 9 =
  34. 34.196 − 99 =
  35. 35.43 + 19 =
  36. 36.75 + 19 =
  37. 37.27 + 19 =
  38. 38.22 + 29 =
  39. 39.12 + 9 =
  40. 40.18 + 9 =

Answer key

  1. 55
  2. 30
  3. 408
  4. 69
  5. 272
  6. 194
  7. 83
  8. 83
  9. 18
  10. 53
  11. 52
  12. 97
  13. 57
  14. 42
  15. 97
  16. 100
  17. 75
  18. 25
  19. 31
  20. 829
  21. 42
  22. 30
  23. 44
  24. 67
  25. 215
  26. 491
  27. 308
  28. 382
  29. 31
  30. 573
  31. 46
  32. 71
  33. 30
  34. 97
  35. 62
  36. 94
  37. 46
  38. 51
  39. 21
  40. 27

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