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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 546 · 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. 1.502 − 99 =
  2. 2.17 + 19 =
  3. 3.69 + 9 =
  4. 4.45 + 29 =
  5. 5.107 − 29 =
  6. 6.71 − 9 =
  7. 7.55 + 9 =
  8. 8.18 − 9 =
  9. 9.37 + 19 =
  10. 10.42 − 19 =
  11. 11.57 + 19 =
  12. 12.588 + 99 =
  13. 13.73 + 29 =
  14. 14.14 − 9 =
  15. 15.86 − 19 =
  16. 16.74 − 19 =
  17. 17.61 + 9 =
  18. 18.34 + 19 =
  19. 19.60 − 9 =
  20. 20.54 − 9 =
  21. 21.773 + 99 =
  22. 22.388 − 99 =
  23. 23.97 − 29 =
  24. 24.486 + 99 =
  25. 25.79 − 9 =
  26. 26.59 − 19 =
  27. 27.312 − 99 =
  28. 28.83 − 9 =
  29. 29.530 − 99 =
  30. 30.46 + 19 =
  31. 31.42 + 9 =
  32. 32.225 − 99 =
  33. 33.58 + 9 =
  34. 34.47 + 19 =
  35. 35.500 + 99 =
  36. 36.65 − 9 =
  37. 37.13 + 29 =
  38. 38.525 − 99 =
  39. 39.109 − 29 =
  40. 40.867 − 99 =

Answer key

  1. 403
  2. 36
  3. 78
  4. 74
  5. 78
  6. 62
  7. 64
  8. 9
  9. 56
  10. 23
  11. 76
  12. 687
  13. 102
  14. 5
  15. 67
  16. 55
  17. 70
  18. 53
  19. 51
  20. 45
  21. 872
  22. 289
  23. 68
  24. 585
  25. 70
  26. 40
  27. 213
  28. 74
  29. 431
  30. 65
  31. 51
  32. 126
  33. 67
  34. 66
  35. 599
  36. 56
  37. 42
  38. 426
  39. 80
  40. 768

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