InterviewSolution
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If `^n+2C_8:^(n-2)P_4: 57 : 16 ,`find `ndot` |
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Answer» `.^(n+2)C_(8):^(n-2)P_(4) = 57:16` `(.^(n+2)C_(8))/(.^(n-2)P_(4)) = (57)/(16)` `rArr ((n+1)!)/(8!(n-6)!).((n-6)!)/((n-2)!) = (57)/(16)` `rArr ((n+2)(n+1)n(n-1)(n-2)!)/((n-2)!) =(57)/(16) xx 8!` `rArr (n+2)(n+1)n(n-1)` `= (57 xx 1 xx 2 xx 3xx 4xx 5xx 6 xx7xx8)/(16)` `rArr (n+2) (n+1).n(n-1) = 21 xx 20 xx 19 xx 18` `rArr n = 19` (on comparison). |
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