A shopkeeper increases the price of an object by 40% and then sells it at 25% discount on the marked price. If the selling price of such an object be Rs. 2100, its cost price for the shopkeeper was?

Let cost price of the article is 100
So, marked price = 140% of 100
$$ = \frac{{140}}{{100}} \times 100 = 140$$
Now, give 25% discount
So, Selling price
$$\eqalign{ & = 140 - 25\% {\text{ of 140}} \cr & = 140 - \frac{1}{4} \times 140 = 105 \cr & 105 \to 2100 \cr & 1 \to 20 \cr & 100 \to 20 \times 100 \cr & \,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}{\text{. }}2000 \cr} $$