'Amit' purchased 'x' articles at the rate of Rs. 80 per

Solution

According to the question, Cost price of 'x' articles = Rs. 80x Selling price of last article = 2 X x = Rs. '2x' {Since, selling price of first article is Rs. 2, second article is Rs. '4', third article is Rs. '6'} Now, 2 + 4 + 6 + .... + 2x = 1.5 X 80x Or, 2(1 + 2 + 3 + .... + x) = 120x Or, (2/2) X {x(x + 1) } = 120x Or, x² + x = 120x Or, x² - 119x = 0 Or, x(x - 119) = 0 Or, x = 119 Therefore, number of articles purchased by 'Bunti' = (x + 6) = 125 Required selling price = 1.8 x 125 x 40 = Rs. 9000