An item when sold for Rs. 1690 earned 30% profit on the cost price. Then the cost price is = ?

Answer: Option C

Let the cost price is x
According to question
$$\begin{array}{rl}& \Rightarrow x\times \frac{100+30}{100}=1690\\ & \Rightarrow x\times \frac{130}{100}=1690\\ & \therefore x=\frac{1690\times 100}{130}\\ & =\text{Rs}\text{.}1300\end{array}$$