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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 597 · 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. 1.57 − 19 =
  2. 2.13 − 9 =
  3. 3.833 − 99 =
  4. 4.431 − 99 =
  5. 5.27 + 29 =
  6. 6.109 − 29 =
  7. 7.20 + 29 =
  8. 8.18 + 19 =
  9. 9.35 + 9 =
  10. 10.150 − 99 =
  11. 11.28 − 9 =
  12. 12.298 + 99 =
  13. 13.83 − 29 =
  14. 14.17 − 9 =
  15. 15.63 − 29 =
  16. 16.27 + 9 =
  17. 17.357 + 99 =
  18. 18.249 + 99 =
  19. 19.53 − 9 =
  20. 20.34 − 19 =
  21. 21.54 − 19 =
  22. 22.477 − 99 =
  23. 23.65 + 19 =
  24. 24.44 + 9 =
  25. 25.21 + 29 =
  26. 26.91 − 19 =
  27. 27.30 + 29 =
  28. 28.896 − 99 =
  29. 29.57 + 9 =
  30. 30.81 − 29 =
  31. 31.87 − 9 =
  32. 32.79 + 29 =
  33. 33.41 + 29 =
  34. 34.719 + 99 =
  35. 35.201 − 99 =
  36. 36.31 + 9 =
  37. 37.310 − 99 =
  38. 38.561 + 99 =
  39. 39.65 − 29 =
  40. 40.55 + 19 =

Answer key

  1. 38
  2. 4
  3. 734
  4. 332
  5. 56
  6. 80
  7. 49
  8. 37
  9. 44
  10. 51
  11. 19
  12. 397
  13. 54
  14. 8
  15. 34
  16. 36
  17. 456
  18. 348
  19. 44
  20. 15
  21. 35
  22. 378
  23. 84
  24. 53
  25. 50
  26. 72
  27. 59
  28. 797
  29. 66
  30. 52
  31. 78
  32. 108
  33. 70
  34. 818
  35. 102
  36. 40
  37. 211
  38. 660
  39. 36
  40. 74

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