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I'm studying for my finals and I came across these questions:

Determine the value of the following expressions:

a) $|\{a,b,c,d,e\}\cap \{c,d,e,f,g\}|=$

b) $|\{(a,b,c,d,e\}\cap\{c,d,e,f,g\})\cup\{l,c,e,g,i\}|=$

c) $|\{\ldots,-3,-2,-1,0,1,2,3\} \cap \{-1,0,1,2,3,4,\ldots\}|=$

Is it correct to say that these are the answers for the following:

a) 3 (c,d,e)

b) 7 (d,e,c,l,i,e,g)

c) 5 (-1,0,1,2,3)

because this | | notation means the number of elements..

Thanks in advance!!

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In $b$ you have to counted $e$ only once otherwise you are right. – Kns Apr 20 '12 at 15:42
up vote 0 down vote accepted

For b you have counted e twice. But you obviously are thinking about it correctly.

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Thanks for the reply :) – Xabi Apr 20 '12 at 15:43

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