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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 466 · 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. 1.60 − 29 =
  2. 2.267 + 99 =
  3. 3.230 − 99 =
  4. 4.78 − 9 =
  5. 5.91 − 29 =
  6. 6.484 + 99 =
  7. 7.45 + 9 =
  8. 8.19 − 9 =
  9. 9.54 + 9 =
  10. 10.64 + 29 =
  11. 11.565 + 99 =
  12. 12.634 + 99 =
  13. 13.547 − 99 =
  14. 14.520 − 99 =
  15. 15.403 + 99 =
  16. 16.19 + 19 =
  17. 17.64 − 19 =
  18. 18.52 + 19 =
  19. 19.65 − 9 =
  20. 20.293 + 99 =
  21. 21.661 + 99 =
  22. 22.236 − 99 =
  23. 23.35 − 19 =
  24. 24.61 − 9 =
  25. 25.12 + 9 =
  26. 26.656 − 99 =
  27. 27.820 − 99 =
  28. 28.73 − 29 =
  29. 29.44 + 9 =
  30. 30.22 − 9 =
  31. 31.204 + 99 =
  32. 32.38 + 29 =
  33. 33.19 + 9 =
  34. 34.89 − 29 =
  35. 35.21 + 19 =
  36. 36.46 − 9 =
  37. 37.29 + 19 =
  38. 38.294 + 99 =
  39. 39.15 + 9 =
  40. 40.24 + 29 =

Answer key

  1. 31
  2. 366
  3. 131
  4. 69
  5. 62
  6. 583
  7. 54
  8. 10
  9. 63
  10. 93
  11. 664
  12. 733
  13. 448
  14. 421
  15. 502
  16. 38
  17. 45
  18. 71
  19. 56
  20. 392
  21. 760
  22. 137
  23. 16
  24. 52
  25. 21
  26. 557
  27. 721
  28. 44
  29. 53
  30. 13
  31. 303
  32. 67
  33. 28
  34. 60
  35. 40
  36. 37
  37. 48
  38. 393
  39. 24
  40. 53

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