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Topic: In how many ways......???
Replies: 5   Last Post: Dec 15, 2013 9:31 PM

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Posts: 6
From: Tokyo
Registered: 12/12/13
In how many ways......???
Posted: Dec 12, 2013 1:50 AM
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Let $S=\{a,b,c,d,e,f\}$. In how many ways can one select two subsets (not necessarily distinct) of $S$ so that their union is $S$?
Note:The order of selection does not matter. For example, $\{a,c,e\},\{b,c,d,f\}$ and $\{b,c,d,f\},\{a,c,e\}$ are counted as same selection.

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