Question

If y varies directly as x and y=3 when x=12, what is the value of when x=18

Answer 1

1/4(18)

Explanation:

Answer 2

`\bf \qquad \qquad \textit{direct proportional variation}\\\\ \textit{\underline{y} varies directly with \underline{x}}\qquad \qquad y=kx\impliedby \begin{array}{llll} k=constant\ of\\ \qquad variation \end{array}\\\\ -------------------------------\\\\ \textit{we also know that } \begin{cases} y=3\\ x=12 \end{cases}\implies 3=k12\implies \cfrac{3}{12}=k \\\\\\ \cfrac{1}{4}=k\qquad therefore\qquad \boxed{y=\cfrac{1}{4}x} \\\\\\ \textit{when x = 18, what is \underline{y}?}\qquad y=\cfrac{1}{4}(18)`