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Home  >>  CBSE XI  >>  Math  >>  Permutations and Combinations
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If $189C_{35}+189C_x=190C_x$ then $x$ is equal to

$\begin{array}{1 1}(A)\;34\\(B)\;35\\(C)\;36\\(D)\;37\end{array} $

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1 Answer

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  • $(n+1)C_r=nC_r+nC_{r-1}$
Since $190C_x=189C_x+189C_{x-1}$
$\Rightarrow 189C_x=189C_{x-1}$
$x-1=35$
$x=36$
Hence (C) is the correct answer.
answered Jun 20, 2014 by sreemathi.v
 

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