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Re: m12#23 - Number System [#permalink]
12 Jun 2010, 07:51

Expert's post

ykaiim wrote:

How many subsets of \((a,b,c,d)\) including both \(a\) and \(c\) and (order of elements does not matter) are there?

A) 3 B) 4 C) 5 D) 6 E) 7

OA is B and OE is: Here are the four subsets: \((a,c)(a,c,b)(a,c,d)(a,c,b,d)\)

I want to know whether \((a)\) and \((c)\) are valid subsets or not?

Generally \((a)\) and \((c)\) are valid subsets of the set \((a,b,c,d)\), but for this question we are looking for subsets that include both \(a\) and \(c\).