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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 671 · 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. 1.277 + 99 =
  2. 2.256 + 99 =
  3. 3.79 + 9 =
  4. 4.303 + 99 =
  5. 5.24 + 19 =
  6. 6.15 + 29 =
  7. 7.74 + 9 =
  8. 8.60 − 29 =
  9. 9.28 − 9 =
  10. 10.31 − 9 =
  11. 11.36 − 9 =
  12. 12.37 + 9 =
  13. 13.14 + 9 =
  14. 14.16 − 9 =
  15. 15.468 + 99 =
  16. 16.88 − 29 =
  17. 17.71 − 9 =
  18. 18.48 − 9 =
  19. 19.484 − 99 =
  20. 20.60 − 19 =
  21. 21.642 + 99 =
  22. 22.21 + 29 =
  23. 23.51 − 29 =
  24. 24.549 + 99 =
  25. 25.75 − 29 =
  26. 26.14 + 29 =
  27. 27.23 − 19 =
  28. 28.83 − 9 =
  29. 29.39 − 19 =
  30. 30.42 − 29 =
  31. 31.12 + 19 =
  32. 32.13 + 29 =
  33. 33.56 − 19 =
  34. 34.23 + 29 =
  35. 35.87 − 29 =
  36. 36.570 + 99 =
  37. 37.95 − 29 =
  38. 38.49 − 9 =
  39. 39.72 − 29 =
  40. 40.32 + 9 =

Answer key

  1. 376
  2. 355
  3. 88
  4. 402
  5. 43
  6. 44
  7. 83
  8. 31
  9. 19
  10. 22
  11. 27
  12. 46
  13. 23
  14. 7
  15. 567
  16. 59
  17. 62
  18. 39
  19. 385
  20. 41
  21. 741
  22. 50
  23. 22
  24. 648
  25. 46
  26. 43
  27. 4
  28. 74
  29. 20
  30. 13
  31. 31
  32. 42
  33. 37
  34. 52
  35. 58
  36. 669
  37. 66
  38. 40
  39. 43
  40. 41

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