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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 291 · 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. 1.49 + 9 =
  2. 2.41 − 29 =
  3. 3.20 − 9 =
  4. 4.35 − 19 =
  5. 5.879 − 99 =
  6. 6.57 + 19 =
  7. 7.76 − 19 =
  8. 8.58 − 9 =
  9. 9.15 + 9 =
  10. 10.74 − 9 =
  11. 11.82 − 9 =
  12. 12.27 − 19 =
  13. 13.577 − 99 =
  14. 14.716 + 99 =
  15. 15.409 − 99 =
  16. 16.16 + 9 =
  17. 17.236 − 99 =
  18. 18.51 + 19 =
  19. 19.36 + 19 =
  20. 20.472 + 99 =
  21. 21.567 + 99 =
  22. 22.57 − 29 =
  23. 23.97 − 19 =
  24. 24.627 + 99 =
  25. 25.25 + 9 =
  26. 26.55 − 29 =
  27. 27.79 − 29 =
  28. 28.60 + 9 =
  29. 29.212 + 99 =
  30. 30.68 + 29 =
  31. 31.28 + 9 =
  32. 32.253 + 99 =
  33. 33.654 + 99 =
  34. 34.416 + 99 =
  35. 35.607 − 99 =
  36. 36.65 − 19 =
  37. 37.37 − 9 =
  38. 38.64 + 29 =
  39. 39.37 − 19 =
  40. 40.293 + 99 =

Answer key

  1. 58
  2. 12
  3. 11
  4. 16
  5. 780
  6. 76
  7. 57
  8. 49
  9. 24
  10. 65
  11. 73
  12. 8
  13. 478
  14. 815
  15. 310
  16. 25
  17. 137
  18. 70
  19. 55
  20. 571
  21. 666
  22. 28
  23. 78
  24. 726
  25. 34
  26. 26
  27. 50
  28. 69
  29. 311
  30. 97
  31. 37
  32. 352
  33. 753
  34. 515
  35. 508
  36. 46
  37. 28
  38. 93
  39. 18
  40. 392

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