JEE Main 2021 — Sets And Relations Question with Solution
From: JEE Main 2021 (Online) 16th March Evening Shift
Question
Let A = {2, 3, 4, 5, ....., 30} and '' be an equivalence relation on A A, defined by (a, b) (c, d), if and only if ad = bc. Then the number of ordered pairs which satisfy this equivalence relation with ordered pair (4, 3) is equal to :
Choose an option
Show full solutionCorrect option: D
Correct answer
D7
Step-by-step explanation
ad = bc
(a, b) R (4, 3) 3a = 4b
a = b
b must be multiple of 3
b = {3, 6, 9 ..... 30}
(a, b) = {(4, 3), (8, 16), (12, 9), (16, 12), (20, 15), (24, 18), (28, 21)}
7 ordered pair
(a, b) R (4, 3) 3a = 4b
a = b
b must be multiple of 3
b = {3, 6, 9 ..... 30}
(a, b) = {(4, 3), (8, 16), (12, 9), (16, 12), (20, 15), (24, 18), (28, 21)}
7 ordered pair
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This is a previous-year question from JEE Main 2021, covering the Sets And Relations chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.