Question

Let A = {1, 2, 3, 4, 5, 6, 7} and B = {3, 6, 7, 9}. Then the number of elements in the set {C ⊆ A :Cߏ∩B ≠ φ} is _____________.

Answer 1

The correct answer is 112
As Cߏ∩B≠φ, c must be not be formed by {1, 2, 4, 5}
∴ Number of subsets of A = 27 = 128
and number of subsets formed by {1, 2, 4, 5} = 16
∴ Required no. of subsets = 27 – 24 = 128 – 16
= 112