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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 334 · 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. 1.79 + 29 =
  2. 2.53 + 19 =
  3. 3.15 + 9 =
  4. 4.24 + 19 =
  5. 5.37 + 19 =
  6. 6.636 − 99 =
  7. 7.25 − 19 =
  8. 8.50 + 9 =
  9. 9.69 − 9 =
  10. 10.69 + 9 =
  11. 11.27 − 9 =
  12. 12.49 + 9 =
  13. 13.109 + 99 =
  14. 14.51 − 19 =
  15. 15.51 + 9 =
  16. 16.78 + 9 =
  17. 17.51 + 29 =
  18. 18.14 + 29 =
  19. 19.394 − 99 =
  20. 20.67 + 29 =
  21. 21.76 + 29 =
  22. 22.13 + 29 =
  23. 23.71 + 19 =
  24. 24.64 + 29 =
  25. 25.338 − 99 =
  26. 26.40 + 29 =
  27. 27.92 − 29 =
  28. 28.719 − 99 =
  29. 29.75 + 29 =
  30. 30.223 + 99 =
  31. 31.24 + 9 =
  32. 32.70 + 19 =
  33. 33.330 − 99 =
  34. 34.32 + 29 =
  35. 35.73 + 29 =
  36. 36.32 + 19 =
  37. 37.41 − 29 =
  38. 38.78 + 29 =
  39. 39.74 + 19 =
  40. 40.44 + 9 =

Answer key

  1. 108
  2. 72
  3. 24
  4. 43
  5. 56
  6. 537
  7. 6
  8. 59
  9. 60
  10. 78
  11. 18
  12. 58
  13. 208
  14. 32
  15. 60
  16. 87
  17. 80
  18. 43
  19. 295
  20. 96
  21. 105
  22. 42
  23. 90
  24. 93
  25. 239
  26. 69
  27. 63
  28. 620
  29. 104
  30. 322
  31. 33
  32. 89
  33. 231
  34. 61
  35. 102
  36. 51
  37. 12
  38. 107
  39. 93
  40. 53

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