JEE Main 2021MathematicsSets and RelationsMediumMCQ

JEE Main 2021 — Sets and Relations Question with Solution

JEE Main 2021 (16 Mar Shift 2)

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

A=2,3,4,5,…,,30

a,b=c,d⇒ad=bc

4,3=c,d ⇒ 4d=3c

⇒43=cd

cd=43 & c,d∈2,3,……,30

c, d =4,3,8,6,12,9,16,12,20,15,24,18,28,21

No. of ordered pair =7

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About this question

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.