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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 26 · 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. 1.59 − 19 =
  2. 2.23 + 19 =
  3. 3.185 − 99 =
  4. 4.60 + 9 =
  5. 5.262 + 99 =
  6. 6.465 − 99 =
  7. 7.67 + 19 =
  8. 8.18 + 9 =
  9. 9.76 − 19 =
  10. 10.76 + 9 =
  11. 11.658 + 99 =
  12. 12.45 − 29 =
  13. 13.21 − 9 =
  14. 14.44 + 29 =
  15. 15.35 − 19 =
  16. 16.54 + 29 =
  17. 17.25 + 29 =
  18. 18.487 − 99 =
  19. 19.53 + 29 =
  20. 20.355 − 99 =
  21. 21.31 + 19 =
  22. 22.22 − 19 =
  23. 23.880 − 99 =
  24. 24.20 + 29 =
  25. 25.726 + 99 =
  26. 26.41 − 29 =
  27. 27.37 + 9 =
  28. 28.42 + 9 =
  29. 29.298 + 99 =
  30. 30.71 − 9 =
  31. 31.36 − 9 =
  32. 32.77 + 29 =
  33. 33.276 + 99 =
  34. 34.74 + 19 =
  35. 35.866 − 99 =
  36. 36.53 + 9 =
  37. 37.99 − 29 =
  38. 38.52 + 9 =
  39. 39.679 − 99 =
  40. 40.29 − 9 =

Answer key

  1. 40
  2. 42
  3. 86
  4. 69
  5. 361
  6. 366
  7. 86
  8. 27
  9. 57
  10. 85
  11. 757
  12. 16
  13. 12
  14. 73
  15. 16
  16. 83
  17. 54
  18. 388
  19. 82
  20. 256
  21. 50
  22. 3
  23. 781
  24. 49
  25. 825
  26. 12
  27. 46
  28. 51
  29. 397
  30. 62
  31. 27
  32. 106
  33. 375
  34. 93
  35. 767
  36. 62
  37. 70
  38. 61
  39. 580
  40. 20

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