The cost price of a radio is Rs. 600. The 5% of the cost price is charged towards transportation. After adding that, if the net profit to be made is 15%, then the selling price of the radio must be = ?

Answer: Option B

According to the question,
Cost price of the radio = Rs. 600
5% of cost price is charged
$$\begin{array}{rl}& =\frac{5}{100}\times 600\\ & =\text{Rs}\text{. 30}\end{array}$$
∴ Total cost price = 600 + 30 = Rs. 630
To gain 15% then selling price
$$\begin{array}{rl}& =630+\frac{15}{100}\times 630\\ & =\text{Rs}\text{. 724}\text{.50}\end{array}$$