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![[Post New]](/templates/default/images/icon_minipost_new.gif) 15 Mar 2008 20:42:48 IST
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a die is rolled n times find value of n if p(getting 1 is ) = 91/216 ans: 3 i am not getting it. so pls tell me/
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TAARA |
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15 Mar 2008 20:48:21 IST
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p(getting 1)=1-p(never getting 1) 91/216 =1-(5/6)^n (5/6)^n =125/216=(5/6)^3 n=3
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15 Mar 2008 20:49:13 IST
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the question shud be phrased lik: a die is thrown n times..the prob tht in these n times of throwing the prob of gettin one '1' is 91/216
it wud be of the form
1/6[1 + 5/6 + (5/6)^2...n times]=91/216
so
we get 1-(5/6)^n=91/216 so (5/6)^n is 125/216
so n is 3
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Nitwit Blubber Odment Tweak
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