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Home  >>  CBSE XI  >>  Math  >>  Permutations and Combinations
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A committee of 7 has to be formed from 9 boys and 4 girls.In how many ways can this be done when the committee consists of Exactly 3 girls?

$\begin{array}{1 1}(A)\;500\\(B)\;502\\(C)\;504\\(D)\;505\end{array} $

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1 Answer

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  • $C(n,r)=\large\frac{n!}{r!(n-r)!}$
A committee consisting of 3 girls and 4 boys can be formed in $1C_3\times 9C_4$ ways
$\Rightarrow 4C_1\times 9C_4$
$\Rightarrow \large\frac{4}{1}\times \frac{9\times 8\times 7\times 6}{1.2.3.4}$
$\Rightarrow 504$ ways
Hence (C) is the correct answer.
answered May 14, 2014 by sreemathi.v
 

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