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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 231 · 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. 1.370 + 99 =
  2. 2.13 + 29 =
  3. 3.110 + 99 =
  4. 4.24 + 29 =
  5. 5.43 − 9 =
  6. 6.46 − 9 =
  7. 7.105 − 29 =
  8. 8.20 + 29 =
  9. 9.74 + 29 =
  10. 10.524 + 99 =
  11. 11.320 − 99 =
  12. 12.27 − 19 =
  13. 13.690 + 99 =
  14. 14.56 + 29 =
  15. 15.50 + 9 =
  16. 16.63 + 29 =
  17. 17.55 − 29 =
  18. 18.44 − 19 =
  19. 19.28 + 9 =
  20. 20.52 − 9 =
  21. 21.40 + 9 =
  22. 22.70 + 29 =
  23. 23.27 + 29 =
  24. 24.812 − 99 =
  25. 25.42 − 19 =
  26. 26.78 + 9 =
  27. 27.76 − 9 =
  28. 28.33 + 29 =
  29. 29.63 − 9 =
  30. 30.343 − 99 =
  31. 31.89 − 29 =
  32. 32.643 + 99 =
  33. 33.54 − 29 =
  34. 34.35 + 9 =
  35. 35.792 + 99 =
  36. 36.71 − 19 =
  37. 37.12 + 29 =
  38. 38.519 − 99 =
  39. 39.61 − 19 =
  40. 40.26 − 9 =

Answer key

  1. 469
  2. 42
  3. 209
  4. 53
  5. 34
  6. 37
  7. 76
  8. 49
  9. 103
  10. 623
  11. 221
  12. 8
  13. 789
  14. 85
  15. 59
  16. 92
  17. 26
  18. 25
  19. 37
  20. 43
  21. 49
  22. 99
  23. 56
  24. 713
  25. 23
  26. 87
  27. 67
  28. 62
  29. 54
  30. 244
  31. 60
  32. 742
  33. 25
  34. 44
  35. 891
  36. 52
  37. 41
  38. 420
  39. 42
  40. 17

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