An article is sold at a 15% profit. If its cost price decreases by 10% and selling price decreases by Rs. 21, the profit becomes 20%. Find the initial cost price. MCQ with Answer and Explanation

Let initial Cost Price = 100x. Initial Selling Price = 115x. New Cost Price = 90x. New Selling Price = 90x * 1.20 = 108x. Difference = 115x - 108x = 7x. 7x = 21. x = 3. Initial Cost Price = 100 * 3 = 300.