Question

Ali bought 12 similar pencils. if each pencil costs rs. 5 leas, he able to buy 4 more pencils. how much did Ali pay for the 12 pencils

Answer 1

$$\begin{gathered} \mathrm{Suppose}\mathrm{Ali}\mathrm{has}\mathrm{Rs}x\mathrm{by}\mathrm{which}\mathrm{he}\mathrm{can}\mathrm{bought}12\mathrm{pencils}. \\ \mathrm{So},\mathrm{the}\mathrm{cost}\mathrm{of}12\mathrm{pencils}=\mathrm{Rs}x \\ \mathrm{cost}\mathrm{of}1\mathrm{pencil}=\mathrm{Rs}\left(\frac{x}{12}\right) \\ \mathbf{WHEN}\mathbf{}\mathbf{THE}\mathbf{}\mathbf{COST}\mathbf{}\mathbf{OF}\mathbf{}\mathbf{EACH}\mathbf{}\mathbf{PENCIL}\mathbf{}\mathbf{IS}\mathbf{}\mathbf{REDUCED}\mathbf{}\mathbf{BY}\mathbf{}\mathbf{Rs}\mathbf{}\mathbf{5}\mathbf{.}\mathbf{00}\mathbf{}: \\ \mathrm{Cost}\mathrm{of}\mathrm{each}\mathrm{pencil}=\mathrm{Rs}\left(\frac{x}{12}-5\right)=\mathrm{Rs}\left(\frac{x-60}{12}\right) \\ \mathrm{Number}\mathrm{of}\mathrm{pencils}\mathrm{bought}\mathrm{for}\mathrm{Rs}x=\frac{x}{{\displaystyle \frac{x-60}{12}}}=\frac{12x}{x-60} \\ \mathrm{Now},\mathrm{according}\mathrm{to}\mathrm{question}, \\ \frac{12x}{x-60}=16 \\ \Rightarrow 16x-960=12x \\ \Rightarrow 16x-12x=960 \\ \Rightarrow 4x=960 \\ \Rightarrow x=\frac{960}{4}=240 \\ \mathrm{So},\mathrm{the}\mathrm{cost}\mathrm{of}12\mathrm{pencils}=\mathrm{Rs}240 \end{gathered}$$