Question

Given, $f\left(x\right)=$ sum of all natural numbers which can divide $x$ completely, then find : $f\left(3\right)\times f\left(10\right)$

Answer 1

Given that $f\left(x\right)=$ sum of all natural numbers which divide $x$ completely

$f\left(3\right)=$ Sum of all natural numbers which can divide $3$ completely,

So, $1$ and $3$ are the numbers which can divide $3$ completely

$\Rightarrow f\left(3\right)=1+3=4$

$f\left(10\right)=$ Sum of all natural numbers which can divide $10$ completely,

So, $1$, $2$, $5$ and $10$ are the numbers which can divide $10$ completely

$\Rightarrow f\left(10\right)=1+2+5+10=18$

So, $f\left(3\right)\times f\left(10\right)=4\times 18=72$