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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 208 · 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. 1.626 + 99 =
  2. 2.73 − 29 =
  3. 3.95 − 29 =
  4. 4.402 − 99 =
  5. 5.77 + 9 =
  6. 6.57 − 29 =
  7. 7.21 + 19 =
  8. 8.650 + 99 =
  9. 9.109 − 29 =
  10. 10.13 + 19 =
  11. 11.544 + 99 =
  12. 12.74 − 29 =
  13. 13.74 + 9 =
  14. 14.66 − 29 =
  15. 15.78 + 9 =
  16. 16.82 − 29 =
  17. 17.23 + 19 =
  18. 18.256 + 99 =
  19. 19.23 − 19 =
  20. 20.64 + 9 =
  21. 21.640 − 99 =
  22. 22.507 + 99 =
  23. 23.32 + 29 =
  24. 24.85 − 19 =
  25. 25.40 − 29 =
  26. 26.370 + 99 =
  27. 27.65 − 19 =
  28. 28.59 + 9 =
  29. 29.51 − 19 =
  30. 30.52 + 9 =
  31. 31.40 + 9 =
  32. 32.419 + 99 =
  33. 33.153 + 99 =
  34. 34.16 + 9 =
  35. 35.15 + 9 =
  36. 36.23 + 9 =
  37. 37.42 − 29 =
  38. 38.189 − 99 =
  39. 39.98 − 19 =
  40. 40.30 + 9 =

Answer key

  1. 725
  2. 44
  3. 66
  4. 303
  5. 86
  6. 28
  7. 40
  8. 749
  9. 80
  10. 32
  11. 643
  12. 45
  13. 83
  14. 37
  15. 87
  16. 53
  17. 42
  18. 355
  19. 4
  20. 73
  21. 541
  22. 606
  23. 61
  24. 66
  25. 11
  26. 469
  27. 46
  28. 68
  29. 32
  30. 61
  31. 49
  32. 518
  33. 252
  34. 25
  35. 24
  36. 32
  37. 13
  38. 90
  39. 79
  40. 39

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