Answer: 7.5% gain
Explanation:
First find the original price of the article.
Assume this price to be x.
x + (x * 20%) = 480
x + 0.2x = 480
1.2x = 480
x = 480/1.2
x = Rs. 400
Original price is Rs. 400.
If the merchant had sold the article for 430, the percent gain would have been:
= (Selling price - original price) / Original price
= (430 - 400) / 400
= 7.5%