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    • Thread Starter

    In a class of 20 pupils, 7 are left handed, and 13 right handed. 5 pupils are selected at random from the class; the order in which they are chosen is not important.

    i) find no. of possible selections in which 2 of the 5 are LH and 3 are RH.
    I got this to be 7C2 x 13C3 which = 6006.

    ii)find the probability that the sample of 5 will include 2 or fewer who are left handed??
    (The answer is supposed to be 0.793 but im not sure how to get that???)


    One way is to find the no. of selections with zero left handed, then the no. with 1 left-handed and the no. with 2 left-handed (done, 6006). Add together, then divide by the no. of ways of selecting any 5 pupils.
    • Thread Starter

    Wow. got the right answer 1st time
    thank you
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Updated: April 3, 2011

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