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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 489 · 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. 1.192 − 99 =
  2. 2.490 + 99 =
  3. 3.356 + 99 =
  4. 4.90 − 19 =
  5. 5.66 + 9 =
  6. 6.46 − 29 =
  7. 7.14 + 29 =
  8. 8.94 − 29 =
  9. 9.48 − 19 =
  10. 10.57 + 9 =
  11. 11.62 − 19 =
  12. 12.801 − 99 =
  13. 13.24 − 9 =
  14. 14.318 + 99 =
  15. 15.597 − 99 =
  16. 16.89 − 19 =
  17. 17.52 − 29 =
  18. 18.86 − 19 =
  19. 19.53 + 9 =
  20. 20.60 − 9 =
  21. 21.37 + 9 =
  22. 22.44 + 9 =
  23. 23.27 − 19 =
  24. 24.76 − 19 =
  25. 25.16 − 9 =
  26. 26.23 − 9 =
  27. 27.57 − 19 =
  28. 28.23 − 19 =
  29. 29.22 − 9 =
  30. 30.32 − 9 =
  31. 31.51 + 29 =
  32. 32.484 − 99 =
  33. 33.277 − 99 =
  34. 34.24 + 19 =
  35. 35.108 − 29 =
  36. 36.20 − 9 =
  37. 37.333 + 99 =
  38. 38.48 − 29 =
  39. 39.210 + 99 =
  40. 40.223 + 99 =

Answer key

  1. 93
  2. 589
  3. 455
  4. 71
  5. 75
  6. 17
  7. 43
  8. 65
  9. 29
  10. 66
  11. 43
  12. 702
  13. 15
  14. 417
  15. 498
  16. 70
  17. 23
  18. 67
  19. 62
  20. 51
  21. 46
  22. 53
  23. 8
  24. 57
  25. 7
  26. 14
  27. 38
  28. 4
  29. 13
  30. 23
  31. 80
  32. 385
  33. 178
  34. 43
  35. 79
  36. 11
  37. 432
  38. 19
  39. 309
  40. 322

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