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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 928 · 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. 1.83 − 19 =
  2. 2.20 + 9 =
  3. 3.767 − 99 =
  4. 4.78 + 29 =
  5. 5.810 − 99 =
  6. 6.85 − 9 =
  7. 7.35 + 29 =
  8. 8.60 + 19 =
  9. 9.73 − 9 =
  10. 10.62 − 19 =
  11. 11.84 − 9 =
  12. 12.36 + 29 =
  13. 13.304 + 99 =
  14. 14.172 + 99 =
  15. 15.627 + 99 =
  16. 16.42 + 29 =
  17. 17.48 − 19 =
  18. 18.29 − 9 =
  19. 19.31 + 9 =
  20. 20.88 − 29 =
  21. 21.47 + 19 =
  22. 22.294 + 99 =
  23. 23.389 − 99 =
  24. 24.25 + 29 =
  25. 25.28 + 9 =
  26. 26.58 + 9 =
  27. 27.674 + 99 =
  28. 28.309 + 99 =
  29. 29.845 − 99 =
  30. 30.94 − 19 =
  31. 31.56 + 9 =
  32. 32.37 + 29 =
  33. 33.541 + 99 =
  34. 34.56 − 29 =
  35. 35.22 + 29 =
  36. 36.566 + 99 =
  37. 37.55 + 29 =
  38. 38.48 + 29 =
  39. 39.44 + 19 =
  40. 40.31 − 19 =

Answer key

  1. 64
  2. 29
  3. 668
  4. 107
  5. 711
  6. 76
  7. 64
  8. 79
  9. 64
  10. 43
  11. 75
  12. 65
  13. 403
  14. 271
  15. 726
  16. 71
  17. 29
  18. 20
  19. 40
  20. 59
  21. 66
  22. 393
  23. 290
  24. 54
  25. 37
  26. 67
  27. 773
  28. 408
  29. 746
  30. 75
  31. 65
  32. 66
  33. 640
  34. 27
  35. 51
  36. 665
  37. 84
  38. 77
  39. 63
  40. 12

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