if n(A) = 6, n(A intersect B) = 2 and n(A union B) = 11, find n(B).
n(A union B) = n(A) + n(B) - n(A intersect B)
Plugging in our given values, we have:
11 = 6 + n(B) - 2
11 = 4 + n(B)
Subtract 4 from each side:
n(B) = 7
n(A union B) = n(A) + n(B) - n(A intersect B)
Plugging in our given values, we have:
11 = 6 + n(B) - 2
11 = 4 + n(B)
Subtract 4 from each side:
n(B) = 7