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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 807 · 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. 1.779 − 99 =
  2. 2.67 + 19 =
  3. 3.28 + 19 =
  4. 4.99 − 19 =
  5. 5.399 − 99 =
  6. 6.309 + 99 =
  7. 7.14 + 19 =
  8. 8.258 + 99 =
  9. 9.46 − 9 =
  10. 10.32 + 9 =
  11. 11.270 − 99 =
  12. 12.649 − 99 =
  13. 13.591 + 99 =
  14. 14.71 − 19 =
  15. 15.35 + 19 =
  16. 16.79 + 29 =
  17. 17.293 + 99 =
  18. 18.28 + 29 =
  19. 19.20 + 9 =
  20. 20.390 − 99 =
  21. 21.31 − 9 =
  22. 22.527 − 99 =
  23. 23.84 − 19 =
  24. 24.75 + 19 =
  25. 25.74 − 9 =
  26. 26.804 − 99 =
  27. 27.71 − 29 =
  28. 28.70 + 29 =
  29. 29.16 + 9 =
  30. 30.69 + 9 =
  31. 31.127 + 99 =
  32. 32.180 + 99 =
  33. 33.455 + 99 =
  34. 34.830 − 99 =
  35. 35.27 + 9 =
  36. 36.53 − 19 =
  37. 37.364 + 99 =
  38. 38.29 + 29 =
  39. 39.69 − 29 =
  40. 40.507 − 99 =

Answer key

  1. 680
  2. 86
  3. 47
  4. 80
  5. 300
  6. 408
  7. 33
  8. 357
  9. 37
  10. 41
  11. 171
  12. 550
  13. 690
  14. 52
  15. 54
  16. 108
  17. 392
  18. 57
  19. 29
  20. 291
  21. 22
  22. 428
  23. 65
  24. 94
  25. 65
  26. 705
  27. 42
  28. 99
  29. 25
  30. 78
  31. 226
  32. 279
  33. 554
  34. 731
  35. 36
  36. 34
  37. 463
  38. 58
  39. 40
  40. 408

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