Question

out of his total income , Kumar spends 25% on house rent & 80% of the remaining on other expenditure & saves the rest . if he saves Rs 1890 per month , What is his total income

Answer 1

$$\begin{gathered} \mathrm{Let}\mathrm{the}\mathrm{total}\mathrm{monthly}\mathrm{income}\mathrm{of}\mathrm{Kumar}=\mathrm{Rs}\mathrm{x} \\ \mathrm{Money}\mathrm{spent}\mathrm{on}\mathrm{house}\mathrm{rent}=25\%\mathrm{of}\mathrm{x}=\frac{25}{100}\times \mathrm{x}=\mathrm{Rs}\left(\frac{\mathrm{x}}{4}\right) \\ \mathrm{Money}\mathrm{left}=\mathrm{x}-\frac{\mathrm{x}}{4}=\mathrm{Rs}\left(\frac{3\mathrm{x}}{4}\right) \\ \mathrm{Money}\mathrm{spent}\mathrm{on}\mathrm{other}\mathrm{expenditure}=80\%\mathrm{of}\left(\frac{3\mathrm{x}}{4}\right)=\frac{80}{100}\times \frac{3\mathrm{x}}{4}=\mathrm{Rs}\left(\frac{3\mathrm{x}}{5}\right) \\ \mathrm{Money}\mathrm{left}=\frac{3\mathrm{x}}{4}-\frac{3\mathrm{x}}{5}=\frac{15\mathrm{x}-12\mathrm{x}}{20}=\mathrm{Rs}\left(\frac{3\mathrm{x}}{20}\right) \\ \mathrm{Now},\mathrm{it}\mathrm{is}\mathrm{given}\mathrm{that}\mathrm{he}\mathrm{saves}\mathrm{Rs}1890. \\ \mathrm{Now},\mathrm{according}\mathrm{to}\mathrm{question}: \\ \frac{3\mathrm{x}}{20}=1890 \\ \Rightarrow \mathrm{x}=\frac{1890\times 20}{3}=12600 \\ \mathrm{So},\mathrm{total}\mathrm{monthly}\mathrm{income}=\mathrm{Rs}12600 \end{gathered}$$