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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 829 · 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. 1.674 − 99 =
  2. 2.67 + 29 =
  3. 3.28 + 29 =
  4. 4.47 − 29 =
  5. 5.35 − 29 =
  6. 6.70 − 29 =
  7. 7.37 − 19 =
  8. 8.42 + 9 =
  9. 9.404 + 99 =
  10. 10.12 + 29 =
  11. 11.734 + 99 =
  12. 12.683 − 99 =
  13. 13.693 + 99 =
  14. 14.107 − 29 =
  15. 15.18 + 29 =
  16. 16.80 − 29 =
  17. 17.71 + 9 =
  18. 18.76 − 9 =
  19. 19.65 + 29 =
  20. 20.46 − 9 =
  21. 21.89 − 19 =
  22. 22.89 − 9 =
  23. 23.211 − 99 =
  24. 24.28 − 19 =
  25. 25.63 − 29 =
  26. 26.84 − 19 =
  27. 27.275 − 99 =
  28. 28.37 + 9 =
  29. 29.88 − 19 =
  30. 30.22 − 19 =
  31. 31.377 + 99 =
  32. 32.33 + 9 =
  33. 33.16 − 9 =
  34. 34.59 − 29 =
  35. 35.30 + 29 =
  36. 36.69 − 19 =
  37. 37.173 + 99 =
  38. 38.49 + 29 =
  39. 39.22 + 9 =
  40. 40.68 + 19 =

Answer key

  1. 575
  2. 96
  3. 57
  4. 18
  5. 6
  6. 41
  7. 18
  8. 51
  9. 503
  10. 41
  11. 833
  12. 584
  13. 792
  14. 78
  15. 47
  16. 51
  17. 80
  18. 67
  19. 94
  20. 37
  21. 70
  22. 80
  23. 112
  24. 9
  25. 34
  26. 65
  27. 176
  28. 46
  29. 69
  30. 3
  31. 476
  32. 42
  33. 7
  34. 30
  35. 59
  36. 50
  37. 272
  38. 78
  39. 31
  40. 87

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