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If f(x) varies directly with x and f(x)= 70 when x=5 , find the value of f(x) when x=9.XRound you final answer to the nearest whole number.

User Lkdg
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Since f(x) varies directly with x, we can write


f(x)=k\cdot x

where k is the constant of proportionality. We know that when x=5, f(5)=70, then we have


70=k\cdot5

then, k is given as


\begin{gathered} k=(70)/(5) \\ k=14 \end{gathered}

Then, the equation which model the problem is


f(x)=14x

Now, we can substitute x=9 into this result. It yields,


\begin{gathered} f(9)=14(9) \\ f(9)=126 \end{gathered}

Therefore, the answer is 126

User MD Naseem Ashraf
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