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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 183 · 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. 1.22 − 9 =
  2. 2.70 + 19 =
  3. 3.53 − 19 =
  4. 4.45 + 9 =
  5. 5.627 − 99 =
  6. 6.33 − 19 =
  7. 7.31 + 9 =
  8. 8.85 − 19 =
  9. 9.30 − 19 =
  10. 10.200 + 99 =
  11. 11.49 − 9 =
  12. 12.19 − 9 =
  13. 13.49 − 29 =
  14. 14.689 + 99 =
  15. 15.95 − 19 =
  16. 16.212 − 99 =
  17. 17.782 − 99 =
  18. 18.63 + 19 =
  19. 19.47 + 19 =
  20. 20.508 − 99 =
  21. 21.25 + 19 =
  22. 22.221 + 99 =
  23. 23.32 + 9 =
  24. 24.38 + 19 =
  25. 25.67 + 19 =
  26. 26.850 − 99 =
  27. 27.444 − 99 =
  28. 28.257 + 99 =
  29. 29.376 − 99 =
  30. 30.72 + 9 =
  31. 31.14 − 9 =
  32. 32.37 + 19 =
  33. 33.792 + 99 =
  34. 34.315 − 99 =
  35. 35.31 + 19 =
  36. 36.21 − 9 =
  37. 37.543 − 99 =
  38. 38.61 − 29 =
  39. 39.34 + 9 =
  40. 40.98 − 29 =

Answer key

  1. 13
  2. 89
  3. 34
  4. 54
  5. 528
  6. 14
  7. 40
  8. 66
  9. 11
  10. 299
  11. 40
  12. 10
  13. 20
  14. 788
  15. 76
  16. 113
  17. 683
  18. 82
  19. 66
  20. 409
  21. 44
  22. 320
  23. 41
  24. 57
  25. 86
  26. 751
  27. 345
  28. 356
  29. 277
  30. 81
  31. 5
  32. 56
  33. 891
  34. 216
  35. 50
  36. 12
  37. 444
  38. 32
  39. 43
  40. 69

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