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Sets $A$ and $B$, shown in the Venn diagram, are such that the total number of elements in set $A$ is twice the total number of elements in set $B$. Altogether, there are $9$ elements in the union of $A$ and $B$, and their intersection has $3$ elements. What is the total number of elements in set $A$?

 

 Sep 11, 2023
 #1
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n (A U B)  = n (A) + n(B)  - n ( A  ∩ B)

 

      9  =    2B + B     -   3

 

      12  = 3B

 

      12/3 = B =  4

 

      A  =  8

 

 

cool cool cool

 Sep 11, 2023

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