In a sale, perfume is available at a discount of 15% on the selling price. If the perfume's discounted selling price is Rs. 3675.40, what was the original selling price of the perfume?

Let the original S.P. of the perfume be Rs. x.
Then,
$$\eqalign{ & {\text{85}}\% {\text{ of }}x = {\text{3675}}{\text{.40}} \cr & \Rightarrow x{\text{ = }}\left( {\frac{{3675.40 \times 100}}{{85}}} \right) \cr & \,\,\,\,\,\,\,\,\,\,\, = 4324 \cr & \,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}{\text{. }}4324 \cr} $$