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If y varies directly as x, and y = 6 when x= 3, find y when x = 9.
y =when x= 9.

User Vffuunnyy
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1 Answer

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We know that:

- y varies directly as x

- y = 6 when x= 3

And we must find y when x = 9

To find it:

1. we must use that y varies directly as x


y=kx

2. We must find k using that y = 6 when x = 3


\begin{gathered} 6=k\cdot3 \\ k=(6)/(3) \\ \Rightarrow k=2 \end{gathered}

3. Finally, to find y when x = 9 we must replace x = 9 and k = 2 to solve it for y


\begin{gathered} y=2\cdot9 \\ y=18 \end{gathered}

ANSWER:

y = 18 when x = 9

User Dani Mesejo
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