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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 723 · 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. 1.51 + 19 =
  2. 2.23 + 19 =
  3. 3.75 − 19 =
  4. 4.13 + 9 =
  5. 5.52 + 9 =
  6. 6.35 − 29 =
  7. 7.93 − 29 =
  8. 8.74 + 29 =
  9. 9.29 + 29 =
  10. 10.43 + 29 =
  11. 11.66 + 29 =
  12. 12.779 + 99 =
  13. 13.413 + 99 =
  14. 14.54 + 9 =
  15. 15.22 − 9 =
  16. 16.23 + 29 =
  17. 17.33 − 29 =
  18. 18.56 + 19 =
  19. 19.59 − 9 =
  20. 20.37 + 19 =
  21. 21.50 + 19 =
  22. 22.99 − 29 =
  23. 23.55 + 9 =
  24. 24.94 − 29 =
  25. 25.299 + 99 =
  26. 26.32 − 9 =
  27. 27.751 + 99 =
  28. 28.103 − 29 =
  29. 29.81 − 19 =
  30. 30.878 − 99 =
  31. 31.721 + 99 =
  32. 32.66 − 19 =
  33. 33.42 + 9 =
  34. 34.15 + 29 =
  35. 35.292 − 99 =
  36. 36.442 − 99 =
  37. 37.32 − 19 =
  38. 38.87 − 9 =
  39. 39.12 + 19 =
  40. 40.15 − 9 =

Answer key

  1. 70
  2. 42
  3. 56
  4. 22
  5. 61
  6. 6
  7. 64
  8. 103
  9. 58
  10. 72
  11. 95
  12. 878
  13. 512
  14. 63
  15. 13
  16. 52
  17. 4
  18. 75
  19. 50
  20. 56
  21. 69
  22. 70
  23. 64
  24. 65
  25. 398
  26. 23
  27. 850
  28. 74
  29. 62
  30. 779
  31. 820
  32. 47
  33. 51
  34. 44
  35. 193
  36. 343
  37. 13
  38. 78
  39. 31
  40. 6

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