Chapter 1 Class 11 Sets
Serial order wise

Ex 1.6, 5 - If X has 40 elements, X U Y 60 elements, find Y

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Question 5 If X and Y are two sets such that X has 40 elements, X ∪ Y has 60 elements and X ∩ Y has 10 elements, how many elements does Y have? Given n(X) = 40, n(X ∪ Y) = 60, n(X ∩ Y) = 10 We know that: n(X ∪ Y) = n(X) + n(Y) – n(X ∩ Y) 60 = 40 + n(Y) – 10 60 = 40 – 10 + n(Y) 60 = 30 + n(Y) ∴ n(Y) = 60 – (30) n(Y) = 30 Thus, the set Y has 30 elements.

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo