Q7 of 109 Page 1

Let A = {2, 3, 4, 5, …, 17, 18}. Let ‘≃’ be the equivalence relation on A × A, cartesian product of A with itself, defined by (a, b) ≃ (c, d) iff ad = bc. Then, the number of ordered pairs of the equivalence class of (3, 2) is

Let (3,2) ≃ (x,y)

⇒ 3y = 2x


This is possible in the cases:


x = 3, y = 2


x = 6, y = 4


x= 9, y =6


x=12, y = 3


x=15, y = 10


x=18,y=12


Hence total pairs are 6.

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