Inverse Proportion Formula and Examples

$y$ is inversely proportional to $x$, and when $x=4$, $y=10$. What is the formula connecting $y$ and $x$?

$y$ is inversely proportional to $x$, and when $x=3$, $y=15$. What is $y$ when $x=5$?

$y$ is inversely proportional to $x$, and when $x=6$, $y=8$. What is $y$ when $x=12$?

$y$ is inversely proportional to $x^2$, and when $x=2$, $y=18$. What is $y$ when $x=6$?

$y$ is inversely proportional to $x^2$, and when $x=5$, $y=8$. What is $x$ when $y=2$?

$n$ is inversely proportional to $\sqrt{r}$, and when $r=25$, $n=14$. What is $n$ when $r=49$?