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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 262 · 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. 1.54 − 29 =
  2. 2.12 + 19 =
  3. 3.80 − 29 =
  4. 4.65 − 9 =
  5. 5.459 − 99 =
  6. 6.73 − 9 =
  7. 7.21 − 9 =
  8. 8.88 − 19 =
  9. 9.277 + 99 =
  10. 10.44 − 29 =
  11. 11.821 − 99 =
  12. 12.23 + 9 =
  13. 13.12 + 29 =
  14. 14.62 + 29 =
  15. 15.209 + 99 =
  16. 16.50 − 19 =
  17. 17.89 − 29 =
  18. 18.97 − 19 =
  19. 19.218 − 99 =
  20. 20.79 + 19 =
  21. 21.524 + 99 =
  22. 22.56 + 9 =
  23. 23.43 + 29 =
  24. 24.20 − 9 =
  25. 25.462 + 99 =
  26. 26.13 − 9 =
  27. 27.371 + 99 =
  28. 28.24 + 29 =
  29. 29.829 − 99 =
  30. 30.549 + 99 =
  31. 31.61 − 9 =
  32. 32.789 − 99 =
  33. 33.31 − 9 =
  34. 34.14 − 9 =
  35. 35.49 + 19 =
  36. 36.41 − 19 =
  37. 37.85 − 9 =
  38. 38.364 + 99 =
  39. 39.152 − 99 =
  40. 40.38 + 29 =

Answer key

  1. 25
  2. 31
  3. 51
  4. 56
  5. 360
  6. 64
  7. 12
  8. 69
  9. 376
  10. 15
  11. 722
  12. 32
  13. 41
  14. 91
  15. 308
  16. 31
  17. 60
  18. 78
  19. 119
  20. 98
  21. 623
  22. 65
  23. 72
  24. 11
  25. 561
  26. 4
  27. 470
  28. 53
  29. 730
  30. 648
  31. 52
  32. 690
  33. 22
  34. 5
  35. 68
  36. 22
  37. 76
  38. 463
  39. 53
  40. 67

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