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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 131 · 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. 1.66 + 19 =
  2. 2.305 + 99 =
  3. 3.39 − 9 =
  4. 4.34 + 19 =
  5. 5.71 − 9 =
  6. 6.238 − 99 =
  7. 7.38 + 19 =
  8. 8.514 − 99 =
  9. 9.658 − 99 =
  10. 10.98 − 19 =
  11. 11.771 − 99 =
  12. 12.67 − 19 =
  13. 13.61 + 9 =
  14. 14.25 − 19 =
  15. 15.46 + 19 =
  16. 16.24 − 19 =
  17. 17.507 − 99 =
  18. 18.72 + 19 =
  19. 19.29 + 9 =
  20. 20.68 − 9 =
  21. 21.27 + 9 =
  22. 22.64 − 9 =
  23. 23.15 + 29 =
  24. 24.69 + 19 =
  25. 25.76 + 9 =
  26. 26.82 − 9 =
  27. 27.22 − 9 =
  28. 28.57 + 19 =
  29. 29.55 + 19 =
  30. 30.506 − 99 =
  31. 31.65 + 29 =
  32. 32.414 + 99 =
  33. 33.19 + 19 =
  34. 34.73 + 29 =
  35. 35.36 + 29 =
  36. 36.306 + 99 =
  37. 37.542 + 99 =
  38. 38.559 − 99 =
  39. 39.271 − 99 =
  40. 40.699 − 99 =

Answer key

  1. 85
  2. 404
  3. 30
  4. 53
  5. 62
  6. 139
  7. 57
  8. 415
  9. 559
  10. 79
  11. 672
  12. 48
  13. 70
  14. 6
  15. 65
  16. 5
  17. 408
  18. 91
  19. 38
  20. 59
  21. 36
  22. 55
  23. 44
  24. 88
  25. 85
  26. 73
  27. 13
  28. 76
  29. 74
  30. 407
  31. 94
  32. 513
  33. 38
  34. 102
  35. 65
  36. 405
  37. 641
  38. 460
  39. 172
  40. 600

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