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mingshum
Senior Member

USA
29 Posts

 Posted - 01/09/2009 :  19:25:17 Help...can this problem from The Official SAT Study Guide be solved with a Venn diagram?Set X has x members and set Y has y members. Set Z consists of all members that are in either set X or set Y with the exception of the k common members (k >0). Which of the following represents the number of members in set Z? Why is the answer x + y - 2k and not x + y -k?

Ultraglide

299 Posts

 Posted - 01/09/2009 :  22:48:56 When you combine X and Y, the common members are counted twice - once in X and once in Y.

mingshum
Senior Member

USA
29 Posts

 Posted - 01/10/2009 :  07:23:23 Thank you Ultraglide...can't believe I didn't see it.
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