Probability

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a bag contains 9 red marbles and 4 blue marbles. how many clear marbles should be added to the bag so the probibility of drawing a red marble is 3/5?????

  • Probability -

    let the number of clear marbles added be x
    so prob of drawing a red
    = 9/(13+x)

    9/(13+x) = 3/5
    39 + 3x =45
    3x= 6
    x = 2
    2 clears should be added

    check:
    now the number of marbles would be 15
    (9 red, 4 blue, 2 clear)
    prob of a red = 9/15 = 3/5

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