A shopkeeper sold an article for ₹ 6750 after giving a discount of 10% on the labelled price. He would have earned a profit of 50%, had there been no discount. What was the actual percentage of profit earned?

Market price = ₹ P
and SP = P -10% of P = 9P/10
∴ 9P/10 = 6750
⇒ P = 7500
If SP = ₹ Rs.7500, then the CP would have been Rs.5000 due to 50% profit earned by the Shopkeeper.
∴ Actual percentage of profit by selling the article for ₹ 6750
= [(SP - CP)/CP] x 100 = [(6750 - 5000)/5000] x 100
= (1750/5000) x 100
= 35%