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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 207 · 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. 1.29 + 29 =
  2. 2.58 − 9 =
  3. 3.42 − 9 =
  4. 4.37 + 9 =
  5. 5.31 − 9 =
  6. 6.792 + 99 =
  7. 7.41 − 19 =
  8. 8.21 + 19 =
  9. 9.102 − 29 =
  10. 10.406 + 99 =
  11. 11.12 + 29 =
  12. 12.141 + 99 =
  13. 13.379 − 99 =
  14. 14.797 − 99 =
  15. 15.77 + 9 =
  16. 16.578 − 99 =
  17. 17.67 + 19 =
  18. 18.74 + 19 =
  19. 19.873 − 99 =
  20. 20.27 + 9 =
  21. 21.53 + 29 =
  22. 22.16 + 29 =
  23. 23.67 − 19 =
  24. 24.66 − 29 =
  25. 25.560 − 99 =
  26. 26.20 + 9 =
  27. 27.404 + 99 =
  28. 28.39 + 19 =
  29. 29.38 − 19 =
  30. 30.623 + 99 =
  31. 31.275 + 99 =
  32. 32.67 + 9 =
  33. 33.89 − 29 =
  34. 34.55 + 19 =
  35. 35.646 − 99 =
  36. 36.150 − 99 =
  37. 37.59 + 9 =
  38. 38.40 + 19 =
  39. 39.167 − 99 =
  40. 40.21 + 29 =

Answer key

  1. 58
  2. 49
  3. 33
  4. 46
  5. 22
  6. 891
  7. 22
  8. 40
  9. 73
  10. 505
  11. 41
  12. 240
  13. 280
  14. 698
  15. 86
  16. 479
  17. 86
  18. 93
  19. 774
  20. 36
  21. 82
  22. 45
  23. 48
  24. 37
  25. 461
  26. 29
  27. 503
  28. 58
  29. 19
  30. 722
  31. 374
  32. 76
  33. 60
  34. 74
  35. 547
  36. 51
  37. 68
  38. 59
  39. 68
  40. 50

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