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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 992 · 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. 1.661 − 99 =
  2. 2.418 + 99 =
  3. 3.95 − 19 =
  4. 4.109 − 29 =
  5. 5.72 − 9 =
  6. 6.435 + 99 =
  7. 7.29 − 9 =
  8. 8.531 − 99 =
  9. 9.46 − 19 =
  10. 10.292 + 99 =
  11. 11.25 − 9 =
  12. 12.360 − 99 =
  13. 13.14 + 19 =
  14. 14.64 + 29 =
  15. 15.33 + 19 =
  16. 16.15 + 19 =
  17. 17.59 + 19 =
  18. 18.530 − 99 =
  19. 19.72 + 19 =
  20. 20.221 + 99 =
  21. 21.84 − 19 =
  22. 22.61 + 29 =
  23. 23.31 − 19 =
  24. 24.62 + 9 =
  25. 25.79 − 29 =
  26. 26.453 + 99 =
  27. 27.19 + 19 =
  28. 28.37 − 9 =
  29. 29.784 + 99 =
  30. 30.54 − 29 =
  31. 31.25 + 9 =
  32. 32.20 + 29 =
  33. 33.92 − 19 =
  34. 34.61 + 19 =
  35. 35.14 + 29 =
  36. 36.899 − 99 =
  37. 37.43 − 29 =
  38. 38.40 + 9 =
  39. 39.42 + 19 =
  40. 40.746 − 99 =

Answer key

  1. 562
  2. 517
  3. 76
  4. 80
  5. 63
  6. 534
  7. 20
  8. 432
  9. 27
  10. 391
  11. 16
  12. 261
  13. 33
  14. 93
  15. 52
  16. 34
  17. 78
  18. 431
  19. 91
  20. 320
  21. 65
  22. 90
  23. 12
  24. 71
  25. 50
  26. 552
  27. 38
  28. 28
  29. 883
  30. 25
  31. 34
  32. 49
  33. 73
  34. 80
  35. 43
  36. 800
  37. 14
  38. 49
  39. 61
  40. 647

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