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osanseviero

  • one year ago

In a school there are 300 matriculated students (some probability problems)

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  1. osanseviero
    • one year ago
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    210 of those 300 enter the class. 80% of the students that enter the class get good grades, 15% of the students that dont enter the class get good grades

  2. osanseviero
    • one year ago
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    If we chose a random matriculated student, which is the probability of him: 1. Being in the class 2. Don't being in the class and getting good grades 3. Getting good grades

  3. osanseviero
    • one year ago
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    |dw:1383272509491:dw|

  4. osanseviero
    • one year ago
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    a. So 210/300=7/10

  5. HawkCrimson
    • one year ago
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    id say so too

  6. osanseviero
    • one year ago
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    How to do the second?

  7. HawkCrimson
    • one year ago
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    first you find how many students that arnt in the class and are getting gud grades so 90 x 15/100 = 27/2 feel sorry for the student that lost a limb :(

  8. HawkCrimson
    • one year ago
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    cause apparently in that class there is half of a student :'(

  9. osanseviero
    • one year ago
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    wait a sec, please

  10. osanseviero
    • one year ago
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    lol

  11. HawkCrimson
    • one year ago
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    haha xD well there 90 students not in the class, and only 15% of the 90 pass, so 90 x 15/100

  12. osanseviero
    • one year ago
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    90 persons is the 30% of total

  13. osanseviero
    • one year ago
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    are you sure?

  14. HawkCrimson
    • one year ago
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    and then 27/2 / 300 = 9/200

  15. HawkCrimson
    • one year ago
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    umm, i thought i was xD

  16. osanseviero
    • one year ago
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    27/2 is the number of persons that got a good grade

  17. HawkCrimson
    • one year ago
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    and didnt come to class but now idk

  18. HawkCrimson
    • one year ago
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    normally when i got half a person it was a sign that something went wrong but my reasoning makes sense atleast to me lol

  19. osanseviero
    • one year ago
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    Can you repeat your reasoning again? (sorry)

  20. HawkCrimson
    • one year ago
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    90 students are people that do not come to class, 15% of these students are students that do well in exams. therefore 90 x 15/100 = 27/2

  21. osanseviero
    • one year ago
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    Ok, I see now :D

  22. osanseviero
    • one year ago
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    And for the third question?

  23. osanseviero
    • one year ago
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    We know that 9 people that did not entered got good grades. We need to see the ones that did come in

  24. osanseviero
    • one year ago
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    So 80% of 210

  25. HawkCrimson
    • one year ago
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    it would be 210 x 80/100 + 27/2

  26. osanseviero
    • one year ago
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    168 entered and passed, 9 entered and passed, so 176

  27. HawkCrimson
    • one year ago
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    y 9?

  28. osanseviero
    • one year ago
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    the 9 did not enter and did pass*

  29. osanseviero
    • one year ago
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    Sooo...176...and 44/75 (check please)

  30. osanseviero
    • one year ago
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    Probability of entering and getting a good grade

  31. HawkCrimson
    • one year ago
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    but it should be 168 + 27/2 because the number of students that didnt come to class and are getting gud grades are 27/2

  32. HawkCrimson
    • one year ago
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    so 195/2 students pass and the probability of the teacher choosing one is 195/2 /300

  33. osanseviero
    • one year ago
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    Sorry, internet crashed

  34. osanseviero
    • one year ago
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    So 181.5/300

  35. osanseviero
    • one year ago
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    Weird numbers :/

  36. osanseviero
    • one year ago
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    Last one is: Chance of selecting a student that have passed and entered the class

  37. osanseviero
    • one year ago
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    7/10 * 8/10 = 56/100 = 38/50= 19/25

  38. osanseviero
    • one year ago
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    So,...yes?

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