If y varies directly as x, and y is 12 when x is 1.2, what is the constant of variation for this relation? A) 1 B) 10 C) 10.8 D) 14.4
\(\bf \begin{array}{cccccclllll}&\\
\textit{something}&&\textit{varies directly to}&&\textit{something else}\\ \quad \\&\\
\textit{something}&=&{{ \textit{some value}}}&\cdot &\textit{something else}\\ \quad \\&\\
y&=&{{ k}}&\cdot&x&\\
&\\
&& y={{ k }}x&\\
\end{array}& \\\\\\
\textit{we know that }
\begin{cases}
y=12\\
x=1.2
\end{cases}\implies y=kx\implies 12=k\cdot 1.2\)
solve for "k" to find "k", or the "constant of variation"
Direct variation is expressed as y = kx, where k is the constant of variation.
You are given that y = 12 and x = 1.2, so you can find k by substituting this into the direct variation equation:
y = kx
(12) = k(1.2)
k = 10