Medium INTEGER +4 / -1 PYQ · JEE Mains 2023

Let $A=\{1,2,3,5,8,9\}$. Then the number of possible functions $f: A \rightarrow A$ such that $f(m \cdot n)=f(m) \cdot f(n)$ for every $m, n \in A$ with $m \cdot n \in A$ is equal to ___________.

Answer (integer) 432

Solution

<p>$f(1.n)=f(1).f(n)\Rightarrow f(1)=1$.</p> <p>$f(3.3)=(f(3))^2$</p> <p>Hence, the possibilities for $(t(3),(9))$ are $(1,1)$ and $(3,9)$.</p> <p>Other three i.e. $f(2),f(5),f(8)$</p> <p>Can be chosen in 6$^3$ ways.</p> <p>Hence, total number of functions</p> <p>$6^3\times2=432$</p>

About this question

Subject: Mathematics · Chapter: Sets, Relations and Functions · Topic: Sets and Operations

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