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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 859 · 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. 1.23 + 9 =
  2. 2.74 − 9 =
  3. 3.29 + 9 =
  4. 4.804 − 99 =
  5. 5.93 − 29 =
  6. 6.91 − 29 =
  7. 7.77 + 9 =
  8. 8.785 − 99 =
  9. 9.67 − 9 =
  10. 10.478 + 99 =
  11. 11.25 + 9 =
  12. 12.60 − 19 =
  13. 13.65 + 19 =
  14. 14.225 + 99 =
  15. 15.68 − 19 =
  16. 16.46 − 19 =
  17. 17.58 − 29 =
  18. 18.73 + 9 =
  19. 19.68 + 19 =
  20. 20.69 − 9 =
  21. 21.15 + 9 =
  22. 22.44 + 19 =
  23. 23.47 − 29 =
  24. 24.26 + 9 =
  25. 25.19 + 9 =
  26. 26.502 + 99 =
  27. 27.51 + 9 =
  28. 28.235 + 99 =
  29. 29.42 − 9 =
  30. 30.39 + 29 =
  31. 31.32 − 29 =
  32. 32.157 + 99 =
  33. 33.555 − 99 =
  34. 34.75 + 19 =
  35. 35.28 + 9 =
  36. 36.67 + 29 =
  37. 37.725 + 99 =
  38. 38.72 − 9 =
  39. 39.20 + 9 =
  40. 40.576 + 99 =

Answer key

  1. 32
  2. 65
  3. 38
  4. 705
  5. 64
  6. 62
  7. 86
  8. 686
  9. 58
  10. 577
  11. 34
  12. 41
  13. 84
  14. 324
  15. 49
  16. 27
  17. 29
  18. 82
  19. 87
  20. 60
  21. 24
  22. 63
  23. 18
  24. 35
  25. 28
  26. 601
  27. 60
  28. 334
  29. 33
  30. 68
  31. 3
  32. 256
  33. 456
  34. 94
  35. 37
  36. 96
  37. 824
  38. 63
  39. 29
  40. 675

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