Question

If y varies directly as x and when x=4 the value of y is 12 form a linear equation in two variable x and y for this information

Answer 1

$$\begin{gathered} \mathrm{SInce}\mathrm{y}\mathrm{varies}\mathrm{directly}\mathrm{as}\mathrm{x}\mathrm{so} \\ y\mathrm{\alpha }x \\ \mathrm{or}y=\mathrm{k}x \\ \mathrm{for}\mathrm{some}\mathrm{proportionality}\mathrm{constant}\mathrm{k}. \\ \mathrm{Here}y=12\mathrm{and}x=4\mathrm{so} \\ 12=4\mathrm{k} \\ \mathrm{k}=3 \\ \mathrm{putting}\mathrm{this}\mathrm{we}\mathrm{get}, \\ y=3x\mathrm{as}\mathrm{the}\mathrm{required}\mathrm{linear}\mathrm{equation}. \end{gathered}$$