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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 227 · 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. 1.77 + 19 =
  2. 2.49 + 19 =
  3. 3.72 − 9 =
  4. 4.87 − 9 =
  5. 5.47 + 9 =
  6. 6.344 + 99 =
  7. 7.33 − 19 =
  8. 8.170 + 99 =
  9. 9.99 − 19 =
  10. 10.81 − 19 =
  11. 11.62 + 29 =
  12. 12.702 + 99 =
  13. 13.53 − 9 =
  14. 14.36 + 29 =
  15. 15.54 + 9 =
  16. 16.753 − 99 =
  17. 17.16 − 9 =
  18. 18.669 + 99 =
  19. 19.78 − 19 =
  20. 20.23 + 9 =
  21. 21.44 + 9 =
  22. 22.33 + 9 =
  23. 23.46 + 19 =
  24. 24.84 − 9 =
  25. 25.63 − 29 =
  26. 26.680 + 99 =
  27. 27.341 + 99 =
  28. 28.109 − 29 =
  29. 29.38 − 29 =
  30. 30.95 − 29 =
  31. 31.27 − 9 =
  32. 32.68 + 19 =
  33. 33.83 − 9 =
  34. 34.80 + 29 =
  35. 35.47 + 29 =
  36. 36.30 + 19 =
  37. 37.74 + 19 =
  38. 38.43 + 19 =
  39. 39.666 − 99 =
  40. 40.557 − 99 =

Answer key

  1. 96
  2. 68
  3. 63
  4. 78
  5. 56
  6. 443
  7. 14
  8. 269
  9. 80
  10. 62
  11. 91
  12. 801
  13. 44
  14. 65
  15. 63
  16. 654
  17. 7
  18. 768
  19. 59
  20. 32
  21. 53
  22. 42
  23. 65
  24. 75
  25. 34
  26. 779
  27. 440
  28. 80
  29. 9
  30. 66
  31. 18
  32. 87
  33. 74
  34. 109
  35. 76
  36. 49
  37. 93
  38. 62
  39. 567
  40. 458

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