The difference between the selling price of an article at a profit of 15% and at a profit of 10% is Rs. 10. The cost price of the article is = ?

Let cost price of an article be Rs. x
According to the question,
$$\eqalign{ & x + \frac{{15}}{{100}}x - \left( {x + \frac{{10}}{{100}}x} \right) = 10 \cr & \Rightarrow \frac{{15x - 10x}}{{100}} = 10 \cr & \Rightarrow \frac{{5x}}{{100}} = 10 \cr & \Rightarrow 5x = 1000 \cr & \therefore x = 200 \cr} $$
Hence. cost price of an article is Rs. 200