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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 452 · 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. 1.641 + 99 =
  2. 2.76 − 9 =
  3. 3.65 + 29 =
  4. 4.35 + 9 =
  5. 5.50 + 19 =
  6. 6.89 − 9 =
  7. 7.40 + 9 =
  8. 8.14 + 9 =
  9. 9.65 − 19 =
  10. 10.50 − 9 =
  11. 11.70 − 29 =
  12. 12.547 + 99 =
  13. 13.36 + 19 =
  14. 14.33 + 19 =
  15. 15.37 + 29 =
  16. 16.79 − 9 =
  17. 17.136 + 99 =
  18. 18.49 + 29 =
  19. 19.59 + 9 =
  20. 20.28 − 9 =
  21. 21.37 + 19 =
  22. 22.60 + 19 =
  23. 23.30 + 19 =
  24. 24.73 − 9 =
  25. 25.77 − 29 =
  26. 26.50 − 19 =
  27. 27.30 + 9 =
  28. 28.71 − 9 =
  29. 29.54 − 9 =
  30. 30.97 − 19 =
  31. 31.30 − 9 =
  32. 32.19 − 9 =
  33. 33.43 + 29 =
  34. 34.500 − 99 =
  35. 35.667 + 99 =
  36. 36.59 − 29 =
  37. 37.77 − 19 =
  38. 38.721 − 99 =
  39. 39.27 + 9 =
  40. 40.95 − 19 =

Answer key

  1. 740
  2. 67
  3. 94
  4. 44
  5. 69
  6. 80
  7. 49
  8. 23
  9. 46
  10. 41
  11. 41
  12. 646
  13. 55
  14. 52
  15. 66
  16. 70
  17. 235
  18. 78
  19. 68
  20. 19
  21. 56
  22. 79
  23. 49
  24. 64
  25. 48
  26. 31
  27. 39
  28. 62
  29. 45
  30. 78
  31. 21
  32. 10
  33. 72
  34. 401
  35. 766
  36. 30
  37. 58
  38. 622
  39. 36
  40. 76

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