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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 935 · 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. 1.48 + 19 =
  2. 2.285 + 99 =
  3. 3.39 + 29 =
  4. 4.404 − 99 =
  5. 5.108 − 29 =
  6. 6.46 + 9 =
  7. 7.66 + 29 =
  8. 8.57 + 19 =
  9. 9.79 + 29 =
  10. 10.194 − 99 =
  11. 11.71 − 9 =
  12. 12.13 − 9 =
  13. 13.217 + 99 =
  14. 14.38 − 9 =
  15. 15.44 − 29 =
  16. 16.77 − 29 =
  17. 17.85 − 29 =
  18. 18.29 − 9 =
  19. 19.98 − 19 =
  20. 20.73 + 19 =
  21. 21.77 + 29 =
  22. 22.648 − 99 =
  23. 23.38 + 9 =
  24. 24.40 + 29 =
  25. 25.67 − 19 =
  26. 26.348 − 99 =
  27. 27.54 + 9 =
  28. 28.37 − 9 =
  29. 29.59 + 29 =
  30. 30.73 + 9 =
  31. 31.66 − 9 =
  32. 32.35 + 19 =
  33. 33.89 − 29 =
  34. 34.79 + 19 =
  35. 35.44 + 9 =
  36. 36.31 + 9 =
  37. 37.74 + 9 =
  38. 38.65 − 9 =
  39. 39.806 − 99 =
  40. 40.476 − 99 =

Answer key

  1. 67
  2. 384
  3. 68
  4. 305
  5. 79
  6. 55
  7. 95
  8. 76
  9. 108
  10. 95
  11. 62
  12. 4
  13. 316
  14. 29
  15. 15
  16. 48
  17. 56
  18. 20
  19. 79
  20. 92
  21. 106
  22. 549
  23. 47
  24. 69
  25. 48
  26. 249
  27. 63
  28. 28
  29. 88
  30. 82
  31. 57
  32. 54
  33. 60
  34. 98
  35. 53
  36. 40
  37. 83
  38. 56
  39. 707
  40. 377

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