The sum of cost price and marked price of article 'A' and that of article 'B' are Rs. 9,000 and Rs. 12,000, respectively. Articles 'A' and 'B' were marked 25% and 100% above their respective cost prices. If both the articles were sold after allowing a discount of 20%, then find the difference between their selling prices.

Let the cost price of article 'A' be Rs. 'x' Therefore, marked price of article 'A' = 1.25 × x = Rs. '1.25x' According to the question, 1.25x + x = 9000 Or, 2.25x = 9000 Or, x = (9000 / 2.25) = 4000 Marked price of article 'A' = 1.25 × 4000 = Rs. 5000 Selling price of article 'A' = 0.8 × 5000 = Rs. 4000 Similarly, let the cost price of article 'B' be Rs. 'y' Marked price of article 'B' = 2y y + 2y = 12000 Or, 3y = 12000 Or, y = (12000 / 3) = 4000 Marked price of article 'B' = 2 × 4000 = Rs. 8000 Selling price of article 'B' = 0.8 × 8000 = Rs. 6400 Required difference = 6400 − 4000 = Rs. 2400