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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 473 · 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. 1.71 − 19 =
  2. 2.31 + 19 =
  3. 3.71 − 9 =
  4. 4.769 + 99 =
  5. 5.43 − 19 =
  6. 6.28 − 9 =
  7. 7.80 − 19 =
  8. 8.20 − 9 =
  9. 9.51 + 29 =
  10. 10.20 + 9 =
  11. 11.73 − 9 =
  12. 12.30 + 9 =
  13. 13.79 + 29 =
  14. 14.41 + 29 =
  15. 15.74 − 29 =
  16. 16.20 + 19 =
  17. 17.58 + 29 =
  18. 18.46 + 29 =
  19. 19.71 + 19 =
  20. 20.22 − 9 =
  21. 21.40 − 9 =
  22. 22.29 + 29 =
  23. 23.66 + 29 =
  24. 24.118 + 99 =
  25. 25.444 + 99 =
  26. 26.384 + 99 =
  27. 27.98 − 29 =
  28. 28.72 − 19 =
  29. 29.31 − 9 =
  30. 30.25 + 19 =
  31. 31.589 + 99 =
  32. 32.61 − 19 =
  33. 33.44 − 29 =
  34. 34.19 + 9 =
  35. 35.629 + 99 =
  36. 36.67 + 9 =
  37. 37.35 − 19 =
  38. 38.63 + 19 =
  39. 39.362 − 99 =
  40. 40.626 + 99 =

Answer key

  1. 52
  2. 50
  3. 62
  4. 868
  5. 24
  6. 19
  7. 61
  8. 11
  9. 80
  10. 29
  11. 64
  12. 39
  13. 108
  14. 70
  15. 45
  16. 39
  17. 87
  18. 75
  19. 90
  20. 13
  21. 31
  22. 58
  23. 95
  24. 217
  25. 543
  26. 483
  27. 69
  28. 53
  29. 22
  30. 44
  31. 688
  32. 42
  33. 15
  34. 28
  35. 728
  36. 76
  37. 16
  38. 82
  39. 263
  40. 725

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