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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 316 · 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. 1.709 − 99 =
  2. 2.78 + 9 =
  3. 3.45 + 19 =
  4. 4.82 − 29 =
  5. 5.411 + 99 =
  6. 6.416 − 99 =
  7. 7.12 + 29 =
  8. 8.179 − 99 =
  9. 9.65 + 19 =
  10. 10.71 + 9 =
  11. 11.78 − 9 =
  12. 12.185 − 99 =
  13. 13.38 + 29 =
  14. 14.17 − 9 =
  15. 15.56 − 29 =
  16. 16.42 + 19 =
  17. 17.33 + 29 =
  18. 18.350 − 99 =
  19. 19.296 + 99 =
  20. 20.43 − 29 =
  21. 21.38 − 29 =
  22. 22.17 + 29 =
  23. 23.48 − 29 =
  24. 24.289 − 99 =
  25. 25.462 + 99 =
  26. 26.25 + 19 =
  27. 27.37 − 9 =
  28. 28.20 + 9 =
  29. 29.706 − 99 =
  30. 30.46 − 29 =
  31. 31.70 + 29 =
  32. 32.43 + 29 =
  33. 33.471 − 99 =
  34. 34.357 + 99 =
  35. 35.49 − 19 =
  36. 36.37 + 9 =
  37. 37.31 − 9 =
  38. 38.33 + 9 =
  39. 39.25 − 9 =
  40. 40.15 + 29 =

Answer key

  1. 610
  2. 87
  3. 64
  4. 53
  5. 510
  6. 317
  7. 41
  8. 80
  9. 84
  10. 80
  11. 69
  12. 86
  13. 67
  14. 8
  15. 27
  16. 61
  17. 62
  18. 251
  19. 395
  20. 14
  21. 9
  22. 46
  23. 19
  24. 190
  25. 561
  26. 44
  27. 28
  28. 29
  29. 607
  30. 17
  31. 99
  32. 72
  33. 372
  34. 456
  35. 30
  36. 46
  37. 22
  38. 42
  39. 16
  40. 44

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