Question

​In which of the following tables $x$ and $y$ vary directly?​

$x$	$7$	$9$	$13$	$21$	$25$
$y$	$21$	$27$	$39$	$63$	$75$

Answer 1

Step: Check if $x$ and $y$ vary directly​

$x$	$7$	$9$	$13$	$21$	$25$
$y$	$21$	$27$	$39$	$63$	$75$

From the given table we have,

$\frac{x}{y}=\frac{7}{21}=\frac{9}{27}=\frac{13}{39}=\frac{21}{63}=\frac{25}{75}=\frac{1}{3}$

Thus the ratio of corresponding values of $x$ and $y$ is constant and is equal to $\frac{1}{3}$

Hence $x$ and $y$ vary directly with each other.