Question

Aitude in a building with 20 families, it was found that 15 families had members who voted for bjp, and 8 families had members who voted for congress. if there are 2 families such that no one from those families voted, how many families bjp as well as congress voters?

Answer 1

Total no. of families = 20

No. of families do not vote = 2

No. of families voting BJP , say B = 15

No. of families voting BJP congress, say C = 8

So, Total no. of families who had members to vote = 20 – 2 = 18 = n(B U C)

We know that n(B U C) = n(B) + n(C) – n(B ∩ C)

n(B ∩ C) = n(B) + n(C) - n(B U C)

= 15+8-18= 5

So, there are 5 families who had members to vote both BJP and Congress.