A woman sold her earphone for ₹2,000 and got a percentage profit equal to the numerical value of cost price. The cost price of the earphone is:

₹ 500 ₹ 200 ₹ 600 ₹ 400

₹ 400

Let the cost price = x then profit will be = \(\frac{x × x}{100}\) = \(\frac{x^2}{100}\) x + \(\frac{x^2}{100}\) = 2000 x + \(\frac{x^2}{100}\) - 2000 = 0 x2 + 100x - 200000 = 0 x = 400