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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 194 · 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. 1.267 + 99 =
  2. 2.291 − 99 =
  3. 3.20 + 19 =
  4. 4.642 − 99 =
  5. 5.616 + 99 =
  6. 6.68 − 9 =
  7. 7.799 + 99 =
  8. 8.139 + 99 =
  9. 9.21 − 9 =
  10. 10.71 − 9 =
  11. 11.25 − 19 =
  12. 12.56 − 9 =
  13. 13.43 + 29 =
  14. 14.23 + 29 =
  15. 15.413 + 99 =
  16. 16.61 − 29 =
  17. 17.72 + 9 =
  18. 18.869 − 99 =
  19. 19.377 + 99 =
  20. 20.50 + 29 =
  21. 21.86 − 19 =
  22. 22.174 + 99 =
  23. 23.127 + 99 =
  24. 24.49 + 9 =
  25. 25.68 − 19 =
  26. 26.786 + 99 =
  27. 27.38 + 9 =
  28. 28.87 − 29 =
  29. 29.23 − 9 =
  30. 30.41 − 19 =
  31. 31.157 + 99 =
  32. 32.64 + 19 =
  33. 33.34 + 9 =
  34. 34.438 − 99 =
  35. 35.71 + 19 =
  36. 36.597 − 99 =
  37. 37.96 − 19 =
  38. 38.104 − 29 =
  39. 39.26 + 29 =
  40. 40.65 − 9 =

Answer key

  1. 366
  2. 192
  3. 39
  4. 543
  5. 715
  6. 59
  7. 898
  8. 238
  9. 12
  10. 62
  11. 6
  12. 47
  13. 72
  14. 52
  15. 512
  16. 32
  17. 81
  18. 770
  19. 476
  20. 79
  21. 67
  22. 273
  23. 226
  24. 58
  25. 49
  26. 885
  27. 47
  28. 58
  29. 14
  30. 22
  31. 256
  32. 83
  33. 43
  34. 339
  35. 90
  36. 498
  37. 77
  38. 75
  39. 55
  40. 56

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