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anonymous

  • one year ago

ok so, a bag contains 2 white marbles and 7 purple marbles. Two marbles are drawn at random one marbles drawn and replaced. then the second is drawn 1. what is the probability of selecting a purple marble and then a white marble? 2. what is the probability of selecting two white marbles? 3. is there a greater chance of selecting two white marbles in row or two purple marbles in row?

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  1. anonymous
    • one year ago
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    i really need help please i dont understand

  2. Vocaloid
    • one year ago
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    let's break the problem down step by step: 1. how many purple marbles are there? 2. how many total marbles are there?

  3. anonymous
    • one year ago
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    7

  4. Vocaloid
    • one year ago
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    yes, there are 7 purple marbles. how many total marbles are there?

  5. anonymous
    • one year ago
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    9

  6. Vocaloid
    • one year ago
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    Excellent! so what is the probability of getting a purple marble?

  7. anonymous
    • one year ago
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    7/9?

  8. Vocaloid
    • one year ago
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    yes! since the problem says "with replacement" that means that after we put the purple marble back, there are still 7 purple marbles and 2 white marbles. my next question: what is the probability of getting a white marble?

  9. anonymous
    • one year ago
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    2/9

  10. Vocaloid
    • one year ago
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    great, you're doing very well so far! ok, so #1 is asking "what is the probability of getting a purple marble AND a white marble" that means you have to multiply the probability of getting a purple marble, times the probability of getting a white marble

  11. Vocaloid
    • one year ago
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    in other words, the probability of getting purple, then white is: (probability of getting purple)*(probability of getting white)

  12. anonymous
    • one year ago
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    so 7/9 X 2/9?

  13. Vocaloid
    • one year ago
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    yup!

  14. anonymous
    • one year ago
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    ok one sec

  15. anonymous
    • one year ago
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    0.17283950617

  16. Vocaloid
    • one year ago
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    uh, you don't have to do that, you can just leave it as a fraction (7/9)*(2/9) = 14/81, do you agree?

  17. anonymous
    • one year ago
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    oh ok yes

  18. Vocaloid
    • one year ago
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    ok, do you think you can answer #2? 2. what is the probability of selecting two white marbles?

  19. anonymous
    • one year ago
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    ummmmm 7/81?

  20. anonymous
    • one year ago
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    14/81 right

  21. Vocaloid
    • one year ago
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    hint: probability of getting a white marble: 2/9

  22. Vocaloid
    • one year ago
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    no, the answer to number 1 is 14/81, let's find the answer to number 2 using the same logic probability of getting two white marbles = (probability of getting one white marble)*(probability of getting one white marble)

  23. anonymous
    • one year ago
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    ok

  24. anonymous
    • one year ago
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    that would be 1/9 right?

  25. anonymous
    • one year ago
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    si 1/9 x 1/9

  26. Vocaloid
    • one year ago
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    not quite, please remember step 1: what is the probability of getting a white marble? there are 2 white marbles and 9 total marbles, remember?

  27. anonymous
    • one year ago
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    yes

  28. Vocaloid
    • one year ago
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    the probability of getting one white marble is 2/9, do you agree?

  29. anonymous
    • one year ago
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    yes

  30. anonymous
    • one year ago
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    so 2/9 x 2/9???

  31. Vocaloid
    • one year ago
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    YES! excellent! you just finished #2, let's work on #3 what is the probability of getting two purple marbles?

  32. anonymous
    • one year ago
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    so two is 4/81 right

  33. anonymous
    • one year ago
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    ?????

  34. Vocaloid
    • one year ago
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    yes, number 2 is 4/81

  35. Vocaloid
    • one year ago
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    let's work on number 3: what is the probability of getting two purple marbles?

  36. anonymous
    • one year ago
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    7/9 x 7/9?

  37. Vocaloid
    • one year ago
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    great! now, what is the probability of getting two white marbles?

  38. anonymous
    • one year ago
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    49/81 and 4/81?

  39. Vocaloid
    • one year ago
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    great! now, which number is bigger?

  40. anonymous
    • one year ago
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    49/81

  41. Vocaloid
    • one year ago
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    great, so, can you answer question #3 now?

  42. Vocaloid
    • one year ago
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    is there a greater chance of selecting two white marbles in row or two purple marbles in row? purple or white, which one is bigger?

  43. anonymous
    • one year ago
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    yes there is a greater chance a of getting 2 purple marble than 2 white marbles

  44. Vocaloid
    • one year ago
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    AWESOME! you're done ~

  45. anonymous
    • one year ago
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    THANK YOU SO MUCH

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