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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 6 · 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. 1.41 + 9 =
  2. 2.414 + 99 =
  3. 3.23 + 9 =
  4. 4.46 + 29 =
  5. 5.38 − 9 =
  6. 6.229 − 99 =
  7. 7.449 + 99 =
  8. 8.348 + 99 =
  9. 9.55 + 19 =
  10. 10.24 + 19 =
  11. 11.158 − 99 =
  12. 12.25 + 19 =
  13. 13.482 + 99 =
  14. 14.42 − 29 =
  15. 15.35 − 9 =
  16. 16.72 − 9 =
  17. 17.244 − 99 =
  18. 18.89 − 29 =
  19. 19.20 + 29 =
  20. 20.19 + 29 =
  21. 21.514 − 99 =
  22. 22.39 − 19 =
  23. 23.81 − 29 =
  24. 24.566 − 99 =
  25. 25.38 + 9 =
  26. 26.72 + 9 =
  27. 27.96 − 29 =
  28. 28.62 − 19 =
  29. 29.291 + 99 =
  30. 30.706 + 99 =
  31. 31.732 − 99 =
  32. 32.636 + 99 =
  33. 33.771 + 99 =
  34. 34.47 + 9 =
  35. 35.89 − 19 =
  36. 36.66 + 9 =
  37. 37.29 − 9 =
  38. 38.50 + 9 =
  39. 39.62 − 29 =
  40. 40.563 − 99 =

Answer key

  1. 50
  2. 513
  3. 32
  4. 75
  5. 29
  6. 130
  7. 548
  8. 447
  9. 74
  10. 43
  11. 59
  12. 44
  13. 581
  14. 13
  15. 26
  16. 63
  17. 145
  18. 60
  19. 49
  20. 48
  21. 415
  22. 20
  23. 52
  24. 467
  25. 47
  26. 81
  27. 67
  28. 43
  29. 390
  30. 805
  31. 633
  32. 735
  33. 870
  34. 56
  35. 70
  36. 75
  37. 20
  38. 59
  39. 33
  40. 464

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