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Math Help - Probability GCSE

  1. #1
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    Probability GCSE

    Hello everyone, this is probably really easy. I'm revising for my Maths exam tomorrow on data handling and I have this question that I can't seem to get the hang of

    "A cube is drawn at random and replaced 250 times, how many times would you expect a red cube to have been drawn?"

    The probability for picking a red cube is apparently 0.35

    I assumed it was roughly a quarter so I tried doing 250 / 3 and still not the answer I was looking for.

    Can someone help me understand this?

    thanks a lot.
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  2. #2
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    The way in which you have posted the question makes it a bit vague.
    It appears that this binomial.
    The success is getting a red cube with a probability of 0.35 in 250 trials.
    The expected value for a binomial RV is p\cdot N.
    Here p=0.35~\&~N=250.

    Warning: My reading of what you meant may be wildly off.
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  3. #3
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    Yeah I know, it's how it's written on my practice sheet. I don't think it's that, it's just GCSE data handling probability.

    Red - 0.35, Blue - 0.15, Green - 0.2, Black 0.3


    A cube is drawn at random and replaced 250 times (picked up and put back)

    How many times would you expect a red cube to have been drawn?




    That's all it asks, I had trouble trying to work this out, I was told the answer was 88? but I want to understand how to work it out
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  4. #4
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    Quote Originally Posted by Caladbolg View Post
    I was told the answer was 88? but I want to understand how to work it out
    Well (0.35)(250)=?
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  5. #5
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    oh I see, 0.35 x 250 gives you 87.5 and you round it up? or is 87.5 theee answer?
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