If the cost of x metres of wire is d rupees, then what is the cost of y metres of wire at the same rate ?

1 $Rs . (\frac{x y}{d})$ ${\text{ Rs}}{\text{.}}\left( {\frac{{xy}}{d}} \right)$ `
2 $Rs . (x d)$ ${\text{Rs}}{\text{.}}\left( {xd} \right)$
3 $Rs . (y d)$ ${\text{Rs}}{\text{.}}\left( {yd} \right)$
4 $Rs . (\frac{y d}{x})$ ${\text{Rs}}{\text{.}}\left( {\frac{{yd}}{x}} \right)$

Answer:- 1

Explanation:-

Solution:

\begin{aligned} Cost of x metres \\ = Rs . d \\ Coast of 1 metre \\ = Rs . (\frac{d}{x}) \\ Cost of y metres \\ = Rs . (\frac{d}{x} \times y) \\ = Rs . (\frac{y d}{x}) \end{aligned}

$\eqalign{ & {\text{Cost of }}x{\text{ metres}} \cr & = {\text{Rs}}{\text{. }}d \cr & {\text{Coast of 1 metre}} \cr & = {\text{Rs}}{\text{.}}\left( {\frac{d}{x}} \right) \cr & {\text{Cost of }}y{\text{ metres}} \cr & = {\text{Rs}}{\text{.}}\left( {\frac{d}{x} \times y} \right) \cr & = {\text{Rs}}{\text{.}}\left( {\frac{{yd}}{x}} \right) \cr}$