Y varies inversely as x. y is 4 when x is 16. How do you find y if x is 20?

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Answer 1 · 2016-10-18T11:37:15

$y=16/5$

If y varies inversely with x, then y is inversely proportional to x.
$yprop1/x$

Another way to write this is $y=k/x$ where $k$ is a proportionality constant.

First, find $k$ using this equation.

$y=k/x" "$ which gives $k = xy$

$k = 16xx4color(white)(aaa)$ Subsitute $4$ for $y$ and $16$ for $x$ .

$k = 64$

To find $y$ when $x=20$ :

plug $k=64$ and $x=20$ back into the original equation.

$y=k/x$

$y=64/20$

$y=16/5$