A shopkeeper allows a discount of 10% to his customers and still gains 20%, the marked price of the article which costs ₹ 450, is

Here, r = 10% and R = 20%
∴ Required per cent = (r + R)/(100 - r) x 100 %
= [(10 + 20)/(100 - 10)] x 100% = (30 x 100)/90 %
This shows that the marked price of the item is 100/3 % more
than its cost price.
∴ Marked price of the article = (450 x 400)/300
= ₹ 600