By selling a hair oil product for ₹336, the gain is 12%. If the gain is reduced to 9%, find the resultant selling price (in ₹).

Let the cost price of the product be $\text{CP}$.When the gain is 12%, the selling price is $112\%$ of $\text{CP}$.
$$112\%\text{ of CP}=336$$
$$\text{CP}=\frac{336}{1.12}=300$$
If the gain is reduced to 9%, the new selling price will be $109\%$ of $\text{CP}$.
$$\text{New SP}=300\times \frac{109}{100}=3\times 109=327$$