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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 only coffee?(a) 2(b) 3(c) 4(d) 5I have been asked this question in an interview for internship.The question is from Practical Problems on Union and Intersection of Two Sets in chapter Sets of Mathematics – Class 11

Answer»

The correct OPTION is (b) 3

To ELABORATE: We know, n (T ∪ C) = n (T) + n (C) – n (T ∩ C)

Given, n (T ∪ C) = 7, n(T)=4, n(C)=5

7=4+5- n (T ∩ C)

n (T ∩ C) = 2.

n (only C) = n (C ∩ T’) = n (C) – n (T ∩ C) = 5-2=3.

3 members like only coffee.


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