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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 656 · 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. 1.157 − 99 =
  2. 2.81 − 19 =
  3. 3.74 + 29 =
  4. 4.85 − 19 =
  5. 5.51 + 29 =
  6. 6.67 + 19 =
  7. 7.81 − 29 =
  8. 8.18 + 29 =
  9. 9.50 + 19 =
  10. 10.70 − 9 =
  11. 11.36 + 19 =
  12. 12.58 + 9 =
  13. 13.653 + 99 =
  14. 14.286 + 99 =
  15. 15.17 − 9 =
  16. 16.80 − 19 =
  17. 17.253 − 99 =
  18. 18.35 − 19 =
  19. 19.752 − 99 =
  20. 20.78 − 29 =
  21. 21.23 + 9 =
  22. 22.883 − 99 =
  23. 23.49 + 29 =
  24. 24.74 + 19 =
  25. 25.59 + 9 =
  26. 26.67 + 29 =
  27. 27.570 − 99 =
  28. 28.35 − 29 =
  29. 29.231 − 99 =
  30. 30.32 − 29 =
  31. 31.71 − 19 =
  32. 32.292 + 99 =
  33. 33.72 − 9 =
  34. 34.849 − 99 =
  35. 35.82 − 19 =
  36. 36.66 − 9 =
  37. 37.37 + 9 =
  38. 38.16 + 9 =
  39. 39.582 − 99 =
  40. 40.63 − 29 =

Answer key

  1. 58
  2. 62
  3. 103
  4. 66
  5. 80
  6. 86
  7. 52
  8. 47
  9. 69
  10. 61
  11. 55
  12. 67
  13. 752
  14. 385
  15. 8
  16. 61
  17. 154
  18. 16
  19. 653
  20. 49
  21. 32
  22. 784
  23. 78
  24. 93
  25. 68
  26. 96
  27. 471
  28. 6
  29. 132
  30. 3
  31. 52
  32. 391
  33. 63
  34. 750
  35. 63
  36. 57
  37. 46
  38. 25
  39. 483
  40. 34

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