InterviewSolution
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InterviewSolution
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If `.^(2n)C_(4): .^(n)C_(3)=21:1`, then find the value of n.A. 4B. 5C. 6D. 7 |
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Answer» Given, `(.^(2n)C_(4))/(.^(n)C_(3))=(21)/(1)` `.^(2n)C_(4)=21.^(n)C_(3)` `((2n)!)/((2n-4)!4!)=21(n!)/((n-3)!3!)`. `(2n)(2n-1)(2n-2)(2n-3)=84(n)(n-1)(n-2)` `4(2n-1)(2n-3)=84(n-2)`. Frm the options, n=5 satisfies the above equation. |
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