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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 792 · 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. 1.602 + 99 =
  2. 2.324 + 99 =
  3. 3.71 + 9 =
  4. 4.51 + 9 =
  5. 5.268 − 99 =
  6. 6.47 − 19 =
  7. 7.70 + 9 =
  8. 8.72 + 29 =
  9. 9.41 + 19 =
  10. 10.465 + 99 =
  11. 11.550 + 99 =
  12. 12.587 − 99 =
  13. 13.398 − 99 =
  14. 14.70 − 9 =
  15. 15.59 + 9 =
  16. 16.68 − 19 =
  17. 17.48 − 29 =
  18. 18.40 + 29 =
  19. 19.39 + 29 =
  20. 20.45 + 9 =
  21. 21.26 − 19 =
  22. 22.311 + 99 =
  23. 23.53 + 19 =
  24. 24.84 − 29 =
  25. 25.40 − 29 =
  26. 26.17 + 9 =
  27. 27.28 + 9 =
  28. 28.36 − 9 =
  29. 29.514 + 99 =
  30. 30.12 − 9 =
  31. 31.319 + 99 =
  32. 32.830 − 99 =
  33. 33.43 + 9 =
  34. 34.76 + 9 =
  35. 35.215 + 99 =
  36. 36.46 − 19 =
  37. 37.763 + 99 =
  38. 38.68 + 19 =
  39. 39.504 + 99 =
  40. 40.55 − 29 =

Answer key

  1. 701
  2. 423
  3. 80
  4. 60
  5. 169
  6. 28
  7. 79
  8. 101
  9. 60
  10. 564
  11. 649
  12. 488
  13. 299
  14. 61
  15. 68
  16. 49
  17. 19
  18. 69
  19. 68
  20. 54
  21. 7
  22. 410
  23. 72
  24. 55
  25. 11
  26. 26
  27. 37
  28. 27
  29. 613
  30. 3
  31. 418
  32. 731
  33. 52
  34. 85
  35. 314
  36. 27
  37. 862
  38. 87
  39. 603
  40. 26

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