The CP of 25 articles is equal to SP of 20 articles. Find the loss or gain percent.

Step 1: Understand the problem The cost price (CP) of 25 articles is the same as the selling price (SP) of 20 articles. This means that the seller is selling 20 articles for the price he bought 25 articles.

Step 2: Set up the equation Let's assume the cost price of 1 article is $1. Therefore, the cost price of 25 articles is$25. According to the problem, this is also the selling price of 20 articles. So, the selling price of 1 article is $25/20 =$1.25.

Step 3: Calculate the gain The seller is selling each article for $1.25, which he bought for$1. So, the gain per article is $1.25 -$1 = $0.25.

Step 4: Calculate the gain percentage The gain percentage is calculated as (Gain / Cost price) * 100. Substituting the values we get, (0.25 / 1) * 100 = 25%.

So, the seller is making a gain of 25%.