A seller sells an article at Rs. 75 and got profit percent equal to numerical value of its cost price. Find the cost price of article. एक विक्रेता एक वस्तु को 75 रु. में बेचता है और उस वस्तु पर हुआ लाभ प्रतिशत उसके क्रय मूल्य के बराबर है, वस्तु का क्रयमूल्य ज्ञात कीजिये।

Let CP = x. Profit percentage = x (numerical value of cost price). So profit = x% of CP = x × x / 100. Selling Price = CP + Profit = x + x²/100 = 75. This gives the quadratic equation x² + 100x - 7500 = 0. Solving: x = [-100 ± √(10000 + 30000)] / 2 = [-100 ± √40000] / 2 = [-100 ± 200] / 2. Taking positive value: x = (100)/2 = 50. Verification: CP = 50, profit = 50% of 50 = 25, SP = 50 + 25 = 75. The claimed answer B (50) is correct.