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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 968 · 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. 1.77 + 9 =
  2. 2.29 − 9 =
  3. 3.32 − 29 =
  4. 4.15 + 9 =
  5. 5.72 − 29 =
  6. 6.30 + 19 =
  7. 7.18 + 29 =
  8. 8.40 − 19 =
  9. 9.72 − 9 =
  10. 10.28 + 9 =
  11. 11.678 − 99 =
  12. 12.92 − 19 =
  13. 13.22 + 19 =
  14. 14.396 + 99 =
  15. 15.39 + 9 =
  16. 16.29 + 29 =
  17. 17.43 − 19 =
  18. 18.33 − 19 =
  19. 19.95 − 19 =
  20. 20.47 + 9 =
  21. 21.485 + 99 =
  22. 22.297 + 99 =
  23. 23.532 − 99 =
  24. 24.76 + 29 =
  25. 25.438 − 99 =
  26. 26.586 + 99 =
  27. 27.61 + 9 =
  28. 28.405 + 99 =
  29. 29.114 + 99 =
  30. 30.66 + 9 =
  31. 31.63 + 19 =
  32. 32.34 + 19 =
  33. 33.53 + 29 =
  34. 34.31 − 9 =
  35. 35.797 + 99 =
  36. 36.93 − 29 =
  37. 37.56 + 19 =
  38. 38.46 + 29 =
  39. 39.687 + 99 =
  40. 40.83 − 9 =

Answer key

  1. 86
  2. 20
  3. 3
  4. 24
  5. 43
  6. 49
  7. 47
  8. 21
  9. 63
  10. 37
  11. 579
  12. 73
  13. 41
  14. 495
  15. 48
  16. 58
  17. 24
  18. 14
  19. 76
  20. 56
  21. 584
  22. 396
  23. 433
  24. 105
  25. 339
  26. 685
  27. 70
  28. 504
  29. 213
  30. 75
  31. 82
  32. 53
  33. 82
  34. 22
  35. 896
  36. 64
  37. 75
  38. 75
  39. 786
  40. 74

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