The ratio of income and expenditure of a person is $11 : 10$. If he saves ₹ 9000 per annum, his monthly income is

### Concept & Income and Savings Savings is the difference between income and expenditure. When given as a ratio, the difference in the ratio parts represents the savings. It's crucial to match the timeframes (annual vs. monthly). ### Step-by-Step Solution Given: * Ratio of Income to Expenditure = $11 : 10$ * Annual Savings = ₹ 9000 1. Determine the ratio parts for savings: Savings Ratio = Income Ratio - Expenditure Ratio Savings Ratio = $11 - 10 = 1 \text{ part}$ 2. Equate the savings ratio part to the actual savings amount: $1 \text{ part} = 9000 \text{ (Annual)}$ 3. Calculate the annual income (which is 11 parts): Annual Income = $11 \times 9000 = 99000$ 4. Convert the annual income to monthly income: Monthly Income = $\frac{99000}{12}$ Monthly Income = $8250$ ### Exam Strategy & Shortcut Recognize that 1 unit of ratio equals ₹ 9000 annually. Annual income is $11 \times 9000$. Monthly income is simply $\frac{11 \times 9000}{12} = 11 \times 750 = 8250$. ### Common Pitfall Forgetting to convert the annual savings/income into a *monthly* figure, which would lead to incorrect calculations or searching for 99000 in the options. ### Final Answer Therefore, the correct answer is **₹ 8250**.