Identify Given Values

Note down the selling price and the gain percentage from the question: $\text{SP} = \text{Rs. } 450$ and $\text{Gain}\% = 12.5\%$.

$\text{SP} = 450, ext{\text{Gain}}\% = 12.5\%$

Apply Cost Price Formula

Use the standard relationship between Cost Price, Selling Price, and Gain Percentage: $CP = \frac{SP imes 100}{100 + \text{Gain}\%}$.

$CP = \frac{SP imes 100}{100 + ext{\text{Gain}}\%}$

Substitute Values and Simplify

Substitute $\text{SP} = 450$ and $\text{Gain}\% = 12.5$ into the formula: $CP = \frac{450 imes 100}{112.5}$.

$CP = \frac{45000}{112.5}$

Calculate Final Result

Divide 45000 by 112.5 to find the cost price: $CP = \text{Rs. } 400$.

$CP = 400$