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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 141 · 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. 1.37 − 9 =
  2. 2.532 + 99 =
  3. 3.59 − 9 =
  4. 4.37 − 29 =
  5. 5.334 + 99 =
  6. 6.25 + 29 =
  7. 7.100 − 29 =
  8. 8.303 − 99 =
  9. 9.80 − 29 =
  10. 10.30 − 19 =
  11. 11.17 + 19 =
  12. 12.291 − 99 =
  13. 13.719 + 99 =
  14. 14.675 − 99 =
  15. 15.45 − 29 =
  16. 16.641 − 99 =
  17. 17.25 + 9 =
  18. 18.61 − 9 =
  19. 19.557 + 99 =
  20. 20.838 − 99 =
  21. 21.62 + 19 =
  22. 22.59 + 29 =
  23. 23.43 + 19 =
  24. 24.70 − 29 =
  25. 25.80 − 19 =
  26. 26.29 + 19 =
  27. 27.264 − 99 =
  28. 28.222 − 99 =
  29. 29.43 − 29 =
  30. 30.595 + 99 =
  31. 31.870 − 99 =
  32. 32.59 + 9 =
  33. 33.60 − 29 =
  34. 34.22 + 29 =
  35. 35.59 − 29 =
  36. 36.96 − 19 =
  37. 37.13 − 9 =
  38. 38.54 − 9 =
  39. 39.95 − 29 =
  40. 40.41 − 19 =

Answer key

  1. 28
  2. 631
  3. 50
  4. 8
  5. 433
  6. 54
  7. 71
  8. 204
  9. 51
  10. 11
  11. 36
  12. 192
  13. 818
  14. 576
  15. 16
  16. 542
  17. 34
  18. 52
  19. 656
  20. 739
  21. 81
  22. 88
  23. 62
  24. 41
  25. 61
  26. 48
  27. 165
  28. 123
  29. 14
  30. 694
  31. 771
  32. 68
  33. 31
  34. 51
  35. 30
  36. 77
  37. 4
  38. 45
  39. 66
  40. 22

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