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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 727 · 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. 1.607 − 99 =
  2. 2.22 + 19 =
  3. 3.35 − 29 =
  4. 4.43 − 9 =
  5. 5.39 + 9 =
  6. 6.14 + 9 =
  7. 7.19 − 9 =
  8. 8.21 + 9 =
  9. 9.51 − 29 =
  10. 10.41 − 19 =
  11. 11.63 − 9 =
  12. 12.131 + 99 =
  13. 13.199 − 99 =
  14. 14.37 − 29 =
  15. 15.29 + 9 =
  16. 16.24 − 9 =
  17. 17.79 − 19 =
  18. 18.192 − 99 =
  19. 19.721 − 99 =
  20. 20.46 − 29 =
  21. 21.22 + 9 =
  22. 22.687 − 99 =
  23. 23.13 + 9 =
  24. 24.78 + 9 =
  25. 25.42 + 29 =
  26. 26.48 − 29 =
  27. 27.416 − 99 =
  28. 28.102 − 29 =
  29. 29.56 + 9 =
  30. 30.52 − 9 =
  31. 31.32 + 19 =
  32. 32.32 + 9 =
  33. 33.77 − 19 =
  34. 34.61 + 29 =
  35. 35.224 − 99 =
  36. 36.17 + 29 =
  37. 37.59 + 29 =
  38. 38.47 + 9 =
  39. 39.27 − 19 =
  40. 40.20 + 19 =

Answer key

  1. 508
  2. 41
  3. 6
  4. 34
  5. 48
  6. 23
  7. 10
  8. 30
  9. 22
  10. 22
  11. 54
  12. 230
  13. 100
  14. 8
  15. 38
  16. 15
  17. 60
  18. 93
  19. 622
  20. 17
  21. 31
  22. 588
  23. 22
  24. 87
  25. 71
  26. 19
  27. 317
  28. 73
  29. 65
  30. 43
  31. 51
  32. 41
  33. 58
  34. 90
  35. 125
  36. 46
  37. 88
  38. 56
  39. 8
  40. 39

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