InterviewSolution
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InterviewSolution
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A student is allowed to select at most n books from a collection of (2n+1) books. If the total number of ways in which a student selects at least one book is 63. then n equals to - |
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Answer» `(2n+1)C_1+(2n+1)C_2+...+(2n+1)C_n=63` `(2n+1)C_0+(2n+1)C_1+...+(2n+1)C_(2n+1)=2^(2n+1)` `(2n+1)C_0=(2n+1)C_(2n+1)=1` `(2n+1)C_1=(2n+1)C_(2n)` `1+1+2S=2^(2n+1)` `2+2*63=2^(2n+1)` `128=2^(2n+1)` `2^7=2^(2n+1) `2n+1=7` `2n=6` `n=3`. |
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