swerA trader purchases several articles at the rate of 13 for Rs.10 and sells them at the rate of 10 for Rs.13. What is his gain/loss?

To solve this problem, we need to first determine the cost price (CP) and the selling price (SP) of a single article.

Step 1: Determine the Cost Price (CP) of a single article The trader purchases 13 articles for Rs.10. Therefore, the cost price of a single article would be Rs.10/13.

Step 2: Determine the Selling Price (SP) of a single article The trader sells 10 articles for Rs.13. Therefore, the selling price of a single article would be Rs.13/10.

Step 3: Compare the CP and SP to determine the gain or loss If the SP is greater than the CP, the trader makes a gain. If the SP is less than the CP, the trader incurs a loss.

In this case, the SP (Rs.13/10 = Rs.1.3) is greater than the CP (Rs.10/13 = Rs.0.77 approximately). Therefore, the trader makes a gain.

Step 4: Calculate the gain The gain is calculated as the difference between the SP and the CP. Therefore, the gain per article is Rs.1.3 - Rs.0.77 = Rs.0.53 approximately.

So, the trader makes a gain of Rs.0.53 per article.