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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 367 · 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. 1.66 + 9 =
  2. 2.41 − 29 =
  3. 3.69 − 29 =
  4. 4.17 − 9 =
  5. 5.18 + 29 =
  6. 6.29 + 29 =
  7. 7.113 + 99 =
  8. 8.14 + 19 =
  9. 9.43 − 9 =
  10. 10.23 − 9 =
  11. 11.64 − 19 =
  12. 12.76 − 9 =
  13. 13.22 + 29 =
  14. 14.66 + 29 =
  15. 15.27 + 9 =
  16. 16.71 − 9 =
  17. 17.256 − 99 =
  18. 18.782 + 99 =
  19. 19.37 − 29 =
  20. 20.845 − 99 =
  21. 21.438 − 99 =
  22. 22.77 + 19 =
  23. 23.76 + 9 =
  24. 24.785 − 99 =
  25. 25.71 + 19 =
  26. 26.49 − 19 =
  27. 27.39 + 19 =
  28. 28.232 + 99 =
  29. 29.43 + 19 =
  30. 30.23 + 19 =
  31. 31.77 + 9 =
  32. 32.19 − 9 =
  33. 33.69 − 9 =
  34. 34.192 + 99 =
  35. 35.40 + 19 =
  36. 36.48 − 9 =
  37. 37.33 − 9 =
  38. 38.32 + 19 =
  39. 39.96 − 19 =
  40. 40.74 − 19 =

Answer key

  1. 75
  2. 12
  3. 40
  4. 8
  5. 47
  6. 58
  7. 212
  8. 33
  9. 34
  10. 14
  11. 45
  12. 67
  13. 51
  14. 95
  15. 36
  16. 62
  17. 157
  18. 881
  19. 8
  20. 746
  21. 339
  22. 96
  23. 85
  24. 686
  25. 90
  26. 30
  27. 58
  28. 331
  29. 62
  30. 42
  31. 86
  32. 10
  33. 60
  34. 291
  35. 59
  36. 39
  37. 24
  38. 51
  39. 77
  40. 55

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