Given the following definitions: U = {1, 2, 3, 4, 5, 6, 7} A = {1, 2, 4, 5} B = {1, 3, 5, 7} How many elements are in A' ∩ B ?

Question

• Given the following definitions:
  U = {1, 2, 3, 4, 5, 6, 7}

  A = {1, 2, 4, 5}

  B = {1, 3, 5, 7}

  How many elements are in A' ∩ B ?

Answer 1

A' = U - A = {1,2,3,4,5,6,7} - {1,2,4,5} = {3,6,7}

 

The ∩ operation (AND or intersection) includes all elements that are members of both sets (A' and B):

 

A' ∩ B = {3,6,7} ∩ {1,3,5,7} = {3,7}

 

So there are two elements in A' ∩ B.