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    This question is on Q5b on P17 of the Edexcel S2 Pearson Company textbook:

    An archer fires arrows at a target and for each arrow, independently of all the others, the probability that it hits bull's eye is 0.125.

    The archer fires 5 arrows, collects them from a target and fires all 5 again.

    Find the probability that on both occasions fewer than 2 hit the bull's eye.

    Help would be much appreciated. Thanks!
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    P(less than 2 hit the bull's eye)=P(0)+P(1)
    =(1-0.125)^5+0.125(1-0.125)^4

    Then square this value to calculate the probability of it happening on both occasions.
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    Thanks
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    (Original post by Lady_Diamond)
    Thanks
    oops, I made a mistake, I need to multiply the P(2) by 5, because he could hit the board on any of the 5 shots.

    Correction;
    P(less than 2 hit the bull's eye)=P(0)+P(1)
    =(1-0.125)^5+5*0.125(1-0.125)^4
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    Yes I assumed that was a mistake and I have the right answer. Thanks.
 
 
 
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Updated: April 12, 2011
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