The correct option is B 25%
Let the cost price of one article be ₹ 1.
So, the cost price of 25 article be ₹ 25.
Given, the selling price of 20 articles = cost price of 25 articles.
Hence, ₹ 25 = 20 ×selling price of one article.
So, the selling price of 1 article = ₹ 1.25.
Gain %=S.P−CPC.P×100
⇒ Gain %=1.25−11×100=25