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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 958 · 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. 1.40 − 9 =
  2. 2.612 + 99 =
  3. 3.789 − 99 =
  4. 4.682 + 99 =
  5. 5.38 − 19 =
  6. 6.762 − 99 =
  7. 7.76 − 29 =
  8. 8.17 − 9 =
  9. 9.652 + 99 =
  10. 10.82 − 29 =
  11. 11.85 − 19 =
  12. 12.66 − 19 =
  13. 13.294 − 99 =
  14. 14.453 + 99 =
  15. 15.64 + 9 =
  16. 16.39 − 19 =
  17. 17.161 + 99 =
  18. 18.16 + 19 =
  19. 19.596 + 99 =
  20. 20.86 − 29 =
  21. 21.38 + 29 =
  22. 22.25 − 19 =
  23. 23.45 − 29 =
  24. 24.28 + 19 =
  25. 25.58 − 9 =
  26. 26.43 + 9 =
  27. 27.61 + 9 =
  28. 28.289 + 99 =
  29. 29.205 + 99 =
  30. 30.68 − 19 =
  31. 31.94 − 29 =
  32. 32.50 − 9 =
  33. 33.81 − 29 =
  34. 34.20 + 9 =
  35. 35.67 − 19 =
  36. 36.48 − 19 =
  37. 37.28 + 9 =
  38. 38.552 − 99 =
  39. 39.61 − 19 =
  40. 40.73 + 9 =

Answer key

  1. 31
  2. 711
  3. 690
  4. 781
  5. 19
  6. 663
  7. 47
  8. 8
  9. 751
  10. 53
  11. 66
  12. 47
  13. 195
  14. 552
  15. 73
  16. 20
  17. 260
  18. 35
  19. 695
  20. 57
  21. 67
  22. 6
  23. 16
  24. 47
  25. 49
  26. 52
  27. 70
  28. 388
  29. 304
  30. 49
  31. 65
  32. 41
  33. 52
  34. 29
  35. 48
  36. 29
  37. 37
  38. 453
  39. 42
  40. 82

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