In a family of 10 members, 7 of them like tea or coffee, 4 of them like tea and 5 of them like coffee. How many of them like neither tea nor coffee?

Correct Answer: 3
Given, n (T ∪ C) = 7. By de Morgan’s law, n (T’ ∩ C’) = n (T ∪ C)’ = Total – n (T ∪ C) = 10 – 7 = 3. So, 3 members like neither tea nor coffee.