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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 393 · 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. 1.14 + 9 =
  2. 2.21 + 9 =
  3. 3.28 + 9 =
  4. 4.59 − 19 =
  5. 5.57 + 29 =
  6. 6.20 + 29 =
  7. 7.43 − 19 =
  8. 8.40 + 29 =
  9. 9.35 + 19 =
  10. 10.14 + 19 =
  11. 11.102 − 29 =
  12. 12.18 + 29 =
  13. 13.239 − 99 =
  14. 14.42 + 9 =
  15. 15.56 − 29 =
  16. 16.207 − 99 =
  17. 17.53 + 29 =
  18. 18.55 + 9 =
  19. 19.898 − 99 =
  20. 20.87 − 29 =
  21. 21.66 + 19 =
  22. 22.732 + 99 =
  23. 23.655 − 99 =
  24. 24.71 + 9 =
  25. 25.15 − 9 =
  26. 26.76 − 19 =
  27. 27.62 + 9 =
  28. 28.64 − 19 =
  29. 29.324 − 99 =
  30. 30.25 − 19 =
  31. 31.38 − 9 =
  32. 32.23 + 19 =
  33. 33.95 − 29 =
  34. 34.31 − 9 =
  35. 35.70 + 9 =
  36. 36.26 + 19 =
  37. 37.49 − 29 =
  38. 38.42 + 29 =
  39. 39.27 + 29 =
  40. 40.78 − 19 =

Answer key

  1. 23
  2. 30
  3. 37
  4. 40
  5. 86
  6. 49
  7. 24
  8. 69
  9. 54
  10. 33
  11. 73
  12. 47
  13. 140
  14. 51
  15. 27
  16. 108
  17. 82
  18. 64
  19. 799
  20. 58
  21. 85
  22. 831
  23. 556
  24. 80
  25. 6
  26. 57
  27. 71
  28. 45
  29. 225
  30. 6
  31. 29
  32. 42
  33. 66
  34. 22
  35. 79
  36. 45
  37. 20
  38. 71
  39. 56
  40. 59

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