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Home  >>  CBSE XI  >>  Math  >>  Permutations and Combinations
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How many 5-digit telephone numbers can be constructed using the digit 0 to 9 if each number starts with 67 and no digit appear more than once?

$\begin{array}{1 1}(A)\;226\\(B)\;326\\(C)\;336\\(D)\;436\end{array} $

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1 Answer

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There are 10 digits from 0 to 9
I place after 67 can be filled in 8 ways.
II place after 67 can be filled in 7 ways.
III place after 67 can be filled in 6 ways.
$\therefore$ No of telephone numbers that can be constructed.
$\Rightarrow 8\times 7\times 6$
$\Rightarrow 336$
Hence (C) is the correct answer.
answered May 13, 2014 by sreemathi.v
 

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