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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 256 · 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. 1.71 − 29 =
  2. 2.55 − 29 =
  3. 3.601 − 99 =
  4. 4.26 − 9 =
  5. 5.51 + 19 =
  6. 6.680 + 99 =
  7. 7.36 − 9 =
  8. 8.686 + 99 =
  9. 9.54 − 29 =
  10. 10.16 + 19 =
  11. 11.250 + 99 =
  12. 12.27 − 9 =
  13. 13.76 − 19 =
  14. 14.12 + 19 =
  15. 15.49 − 9 =
  16. 16.52 + 19 =
  17. 17.72 − 19 =
  18. 18.698 + 99 =
  19. 19.47 + 9 =
  20. 20.61 + 19 =
  21. 21.52 + 9 =
  22. 22.771 + 99 =
  23. 23.73 − 29 =
  24. 24.61 − 29 =
  25. 25.19 + 9 =
  26. 26.59 + 19 =
  27. 27.50 − 9 =
  28. 28.407 − 99 =
  29. 29.41 + 19 =
  30. 30.50 + 9 =
  31. 31.47 + 29 =
  32. 32.580 − 99 =
  33. 33.534 + 99 =
  34. 34.58 + 9 =
  35. 35.64 + 9 =
  36. 36.705 − 99 =
  37. 37.84 − 19 =
  38. 38.97 − 19 =
  39. 39.745 + 99 =
  40. 40.54 + 9 =

Answer key

  1. 42
  2. 26
  3. 502
  4. 17
  5. 70
  6. 779
  7. 27
  8. 785
  9. 25
  10. 35
  11. 349
  12. 18
  13. 57
  14. 31
  15. 40
  16. 71
  17. 53
  18. 797
  19. 56
  20. 80
  21. 61
  22. 870
  23. 44
  24. 32
  25. 28
  26. 78
  27. 41
  28. 308
  29. 60
  30. 59
  31. 76
  32. 481
  33. 633
  34. 67
  35. 73
  36. 606
  37. 65
  38. 78
  39. 844
  40. 63

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