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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 327 · 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. 2.54 − 19 =
  3. 3.18 + 29 =
  4. 4.162 − 99 =
  5. 5.106 − 29 =
  6. 6.777 + 99 =
  7. 7.495 + 99 =
  8. 8.59 + 19 =
  9. 9.24 − 9 =
  10. 10.89 − 19 =
  11. 11.16 + 29 =
  12. 12.75 + 19 =
  13. 13.185 + 99 =
  14. 14.99 − 29 =
  15. 15.53 + 19 =
  16. 16.79 + 29 =
  17. 17.39 − 29 =
  18. 18.49 − 19 =
  19. 19.40 − 19 =
  20. 20.60 − 29 =
  21. 21.410 − 99 =
  22. 22.47 − 29 =
  23. 23.37 − 29 =
  24. 24.310 + 99 =
  25. 25.66 − 29 =
  26. 26.53 + 29 =
  27. 27.493 + 99 =
  28. 28.131 + 99 =
  29. 29.65 − 9 =
  30. 30.13 + 9 =
  31. 31.73 − 9 =
  32. 32.168 − 99 =
  33. 33.266 + 99 =
  34. 34.65 + 9 =
  35. 35.32 + 19 =
  36. 36.732 + 99 =
  37. 37.20 + 9 =
  38. 38.78 + 19 =
  39. 39.59 − 29 =
  40. 40.41 + 29 =

Answer key

  1. 75
  2. 35
  3. 47
  4. 63
  5. 77
  6. 876
  7. 594
  8. 78
  9. 15
  10. 70
  11. 45
  12. 94
  13. 284
  14. 70
  15. 72
  16. 108
  17. 10
  18. 30
  19. 21
  20. 31
  21. 311
  22. 18
  23. 8
  24. 409
  25. 37
  26. 82
  27. 592
  28. 230
  29. 56
  30. 22
  31. 64
  32. 69
  33. 365
  34. 74
  35. 51
  36. 831
  37. 29
  38. 97
  39. 30
  40. 70

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