If n(A) = 7, n(B) = 6 and n(A n B) = 4, what can you tell about n (A u B)?
We cannot determine the exact value of n(A u B) with the given information, but we can determine a range of possible values.
Using the inclusion-exclusion principle, we know that:
n(A u B) = n(A) + n(B) - n(A n B)
Substituting the given values:
n(A u B) = 7 + 6 - 4 = 9
Therefore, we know that n(A u B) is at least 9. However, we also know that there could be elements in A and B outside of the intersection that are not accounted for in this calculation. Therefore, the actual value of n(A u B) could be greater than 9.