Misc 16 - Chapter 1 Class 12 Relation and Functions (Term 1)
Last updated at Aug. 6, 2021 by Teachoo
Finding number of relations
Last updated at Aug. 6, 2021 by Teachoo
Misc 16 Let A = {1, 2, 3}. Then number of relations containing (1, 2) and (1, 3) which are reflexive and symmetric but not transitive is (A) 1 (B) 2 (C) 3 (D) 4 Total possible pairs = { (1, 1) , (1, 2), (1, 3), (2, 1) , (2, 2), (2, 3), (3, 1) , (3, 2), (3, 3) } Total possible pairs = { (1, 1) , (1, 2), (1, 3), (2, 1) , (2, 2), (2, 3), (3, 1) , (3, 2), (3, 3) } Reflexive means (a, a) should be in relation . So, (1, 1) , (2, 2) , (3, 3) should be in a relation Symmetric means if (a, b) is in relation, then (b, a) should be in relation . So, since (1, 2) is in relation, (2, 1) should be in relation & since (1, 3) is in relation, (3, 1) should be in relation Transitive means if (a, b) is in relation, & (b, c) is in relation, then (a, c) is in relation We need relation which is not transitive. So, we cannot add any more pair in the relation. If we add (2, 3), we need to add (3, 2) for symmetric, but it would become transitive then Relation R1 = { So, there is only 1 possible relation Correct answer is A.