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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 760 · 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. 1.44 + 29 =
  2. 2.71 + 29 =
  3. 3.14 + 29 =
  4. 4.42 + 19 =
  5. 5.105 + 99 =
  6. 6.93 − 29 =
  7. 7.66 − 9 =
  8. 8.77 + 19 =
  9. 9.28 + 9 =
  10. 10.303 + 99 =
  11. 11.53 + 29 =
  12. 12.60 + 9 =
  13. 13.41 − 19 =
  14. 14.33 + 29 =
  15. 15.100 − 29 =
  16. 16.53 − 29 =
  17. 17.40 + 9 =
  18. 18.822 − 99 =
  19. 19.22 + 9 =
  20. 20.65 + 9 =
  21. 21.676 + 99 =
  22. 22.56 + 19 =
  23. 23.46 − 29 =
  24. 24.715 − 99 =
  25. 25.14 + 19 =
  26. 26.77 + 9 =
  27. 27.62 − 9 =
  28. 28.49 + 29 =
  29. 29.29 − 9 =
  30. 30.73 + 29 =
  31. 31.48 − 9 =
  32. 32.32 − 9 =
  33. 33.59 − 9 =
  34. 34.52 + 29 =
  35. 35.57 + 9 =
  36. 36.64 + 9 =
  37. 37.49 + 9 =
  38. 38.72 − 29 =
  39. 39.52 + 19 =
  40. 40.73 + 9 =

Answer key

  1. 73
  2. 100
  3. 43
  4. 61
  5. 204
  6. 64
  7. 57
  8. 96
  9. 37
  10. 402
  11. 82
  12. 69
  13. 22
  14. 62
  15. 71
  16. 24
  17. 49
  18. 723
  19. 31
  20. 74
  21. 775
  22. 75
  23. 17
  24. 616
  25. 33
  26. 86
  27. 53
  28. 78
  29. 20
  30. 102
  31. 39
  32. 23
  33. 50
  34. 81
  35. 66
  36. 73
  37. 58
  38. 43
  39. 71
  40. 82

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