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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 246 · 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. 1.15 + 19 =
  2. 2.58 − 29 =
  3. 3.58 + 19 =
  4. 4.88 − 9 =
  5. 5.789 + 99 =
  6. 6.684 + 99 =
  7. 7.32 − 19 =
  8. 8.98 − 19 =
  9. 9.55 + 19 =
  10. 10.26 + 9 =
  11. 11.20 + 19 =
  12. 12.349 + 99 =
  13. 13.23 + 9 =
  14. 14.39 + 19 =
  15. 15.14 + 19 =
  16. 16.31 + 9 =
  17. 17.47 + 29 =
  18. 18.336 − 99 =
  19. 19.85 − 19 =
  20. 20.370 − 99 =
  21. 21.31 − 19 =
  22. 22.28 − 9 =
  23. 23.24 + 29 =
  24. 24.28 − 19 =
  25. 25.26 + 19 =
  26. 26.21 + 9 =
  27. 27.842 − 99 =
  28. 28.71 + 9 =
  29. 29.251 − 99 =
  30. 30.256 − 99 =
  31. 31.44 − 9 =
  32. 32.86 − 19 =
  33. 33.50 + 29 =
  34. 34.45 − 9 =
  35. 35.54 + 29 =
  36. 36.77 + 19 =
  37. 37.59 + 19 =
  38. 38.40 − 29 =
  39. 39.734 + 99 =
  40. 40.189 − 99 =

Answer key

  1. 34
  2. 29
  3. 77
  4. 79
  5. 888
  6. 783
  7. 13
  8. 79
  9. 74
  10. 35
  11. 39
  12. 448
  13. 32
  14. 58
  15. 33
  16. 40
  17. 76
  18. 237
  19. 66
  20. 271
  21. 12
  22. 19
  23. 53
  24. 9
  25. 45
  26. 30
  27. 743
  28. 80
  29. 152
  30. 157
  31. 35
  32. 67
  33. 79
  34. 36
  35. 83
  36. 96
  37. 78
  38. 11
  39. 833
  40. 90

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