Question

R varies directly as s. Find r when s=13 and k=15

Answer 1

`\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{r varies directly as s}\implies r=ks\qquad k=\textit{constant of variation} \\\\\\ r=ks\qquad \begin{cases} s=13\\ k=15 \end{cases}\implies r=15\cdot 13`