The variables x=2 and y=7 varies directly. How do you write an equation that relates the variables and find y when x=8?

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Answer 1 · 2017-11-29T01:22:00

$y=28$

“The variables $x=2$ and $y=7$ vary directly.”

We can express that as:

$y=mx$

$\rightarrow 7=m\cdot 5$ , where $m$ is the constant of variation (slope).

Now, we need to solve for $m$ :

$7=2m$

Divide both sides by $2$ :

$m=\frac{7}{2}$

Now, we can plug this value, as well $x=8$ , into the next equation to find $y$ :

$y=mx$

$\rightarrow y=\frac{7}{2}\cdot 8$

$\rightarrow y=\frac{56}{2}$

$\rightarrow y=28$

Answer 2 · 2017-11-29T01:23:45

$y =7/2x$
$y(8)=28$

I assume you mean that $x and y$ vary directly and $x=2$ when $y=7$

If so, then we know that:

$y = kx$ for some constant $k$

Since $x=2$ when $y=7$

$:. 7 = kxx2$

$->k=7/2$

Hence, $y =7/2x$ is our required equation.

We are asked to find $y$ when $x=8$

$-> y(8)=7/2xx8 = 7xx4$

$y(8)=28$