Question 611529
Single cards chosen at random are given away with boxes of Weetbix. Each card shows a picture of one of 25 All Blacks. Diane needs just one picture to complete her collection. She buys 3 boxes of Weetbix and looks at all the pictures.
Binomial Problem with n = 3 and p(needed pic) = 1/25 ; P(other pic) = 24/25
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Find the probability that:
a) Diane does not complete her collection.
Ans : (24/25)^3 = 0.885
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b) She has the required picture exactly twice
Ans: 3C2*(1/25)^2(24/25) = binompdf(3,1/25,2) = 0.0046

c) She completes her collection with the second picture she looks at
Ans: (24/25)(1/25) = 24/625
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Cheers,
Stan H.
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