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If a,b, c are in H.P. then `a-(b)/(2),(b)/(2),c-(b)/(2)` are inA. A.P.B. G.P.C. A.G.P.D. H.P. |
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Answer» Correct Answer - B The number of students answering at least r question incorrectly is `2^(n-r)`. `therefore` the number of students answering exactly `r(1lerlen-1)` question incorrectly is `2^(n-r)-2^(n-(r+1))` Also, the number of students answering all question wrongly is `2^(@)=1`. Thus, the total number of wrong answer is : `1(2^(n-1)-2^(n-2))+2(2^(n-2)-2^(n-3))+3(2^(n-3)-2^(n-4))+.......+(n-1)(2^(1)-2^(@))+n(2^(@))` `=2^(n-1)+2^(n-2)+.........+2^(@)=2^(n)-1` Now, `2^(n)-1=4095implies2^(n)=4096=2^(12)impliesn=12`. |
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