The cost of manufacturing an article rose by 18% as a result of the increase in the cost of raw material. A manufacturer revised the selling price of the article so as to maintain the same profit percentage as before. However, he found that he now got ₹ 9 more than the earlier profit by selling each article. What was the earlier profit per article?

### Concept & Proportionality When the cost and the selling price increase such that the profit percentage remains constant, the absolute profit amount increases by the exact same percentage as the cost. $$ \text{New Profit} = \text{Old Profit} \times \left(1 + \frac{\text{Increase \%}}{100}\right) $$ ### Step-by-Step Solution * Let the initial cost price be $C$ and the initial profit be $P$. * The profit percentage is fixed at $\frac{P}{C} \times 100$. * The cost of manufacturing increases by $18\%$. To maintain the same profit percentage, the profit amount must also increase by $18\%$. * The problem states that the new profit is ₹ 9 more than the old profit. * Therefore, $18\%$ of the old profit is exactly equal to this ₹ 9 increase. * $0.18 \times P = 9$ * $P = \frac{9}{0.18} = \frac{900}{18} = 50$. ### Exam Strategy & Shortcut Recognize that if the profit percentage is constant, any percentage increase in cost results in the exact same percentage increase in profit. Directly equate $18\%$ of the original profit to ₹ 9. $100\%$ of profit = $9 \times (\frac{100}{18}) = 50$. ### Common Pitfall A common mistake is assigning the $18\%$ increase to the overall selling price and attempting complex algebraic setups with unknown cost variables, which consumes unnecessary time. ### Final Answer Therefore, the correct answer is **₹ 50**.