If selling price of 10 articles is equal to cost price of 11 articles, then gain is:

The correct choice is: “10%”

Let the cost price of one article be ₹ 1. Then the selling price of 10 articles = cost price of 11 articles = ₹ 11.

Cost price of those 10 articles = ₹ 10, so the gain = ₹ 1 on ₹ 10.

Gain % = (1/10) × 100 = 10%.

“9%” is the gain as a percentage of the selling price (1/11 ≈ 9.09%), but gain percent is always calculated on cost price.