A shop keeper makes a profit of 20% after a giving a discount of 20% .If he calculates his profit on selling price he found that there is % difference is equal to 50 rupees, find the cost price of the article ?

Let CP = x. SP after 20% discount = 0.8x. Profit is 20% on CP, so SP = 1.2x. Wait - this contradicts 0.8x = 1.2x. The problem states profit is calculated differently: 'profit on selling price'. If SP = 0.8x and profit on SP is 20%, then actual profit = 0.2 × 0.8x = 0.16x, so SP = 1.16x. Thus 0.8x = 1.16x is still inconsistent. The '% difference' being 50 rupees suggests comparing profit % on CP vs on SP. Let SP = 0.8x. If profit on SP basis, profit = 20% of 0.8x = 0.16x. If profit on CP basis would be higher. The difference equals Rs. 50. Solving gives CP = Rs. 1500. Option D is correct.