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Thread: too many gumballs

  1. #1
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    Talking too many gumballs

    i am pulling my hair out over this chapter on probability.
    First question which formula do I use to determine this answer.

    A gumball machine contains 300 grape flavored balls, 400 cherry flavored balls, and 500 lemon flavored balls. What is the probability of getting 1 grape ball, 1 cherry ball, and 1 lemon ball if each ball was removed and then replaced before choosing the next from the machine?
    a) 0.0264
    b) 0.0531
    c) 0.0347
    d) 0.0482
    i got answer c
    but i have no clue how the heck i got to that answer.
    p.s i just started learning statisitcs, any info or tools of the trade will be greatly appreciated
    please help
    utterly confused
    Last edited by hilarysears77; 10-07-2005 at 02:04 PM.

  2. #2
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    There are a total of 1200 gumballs.

    If you pick out 1 gumball, the probability of it being grape is the number of grape gumballs divided by total number of all gumballs, so it is

    =300/1200 = 1/4 or 0.25

    Same principle for cherry and lemon:

    cherry = 400/1200 = 1/3 or 0.333

    lemon = 500/1200 = 5/12 or 0.4167

    Now, in order to pick one of each flavor (assuming it is replaced), you are essentially picking 1 grape AND 1 cherry AND 1 lemon.

    Multiply the individual probabilities together, since they are independent* of each other:

    P = 0.25 * 0.333 * 0.4167

    = 0.0347

    *independent means that since you replace each gumball after picking it, that selection has no effect on the probability of any other selection
    Last edited by JohnM; 10-07-2005 at 06:19 PM.

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