The difference between the total sales of some articles if sold for Rs.12 per article instead of Rs.9 per article is Rs.150. If the total costs of these articles is Rs.250, then find the total sales value of 21 articles if profit is 20%.

Let's break down the problem step by step:

Step 1: Find the difference in sales between selling an article for Rs.12 and Rs.9. The difference in price per article is Rs.12 - Rs.9 = Rs.3. The given difference in total sales is Rs.150.

Step 2: Calculate the number of articles sold. To find the number of articles, we divide the difference in total sales by the difference in price per article: Number of articles = Rs.150 / Rs.3 = 50 articles.

Step 3: Calculate the total sales value of 21 articles. Since we know the number of articles sold, we can calculate the total sales value of 21 articles using the ratio: Total sales value of 21 articles = (Total sales value of 50 articles / Number of articles) * 21 Total sales value of 21 articles = (Rs.150 / 50) * 21 = Rs.63 * 21 = Rs.1,323.

Step 4: Calculate the profit. The profit is given as 20% of the total cost, which is Rs.250. Profit = (20/100) * Rs.250 = Rs.50.

Step 5: Calculate the total sales value of 21 articles with profit. To find the total sales value with profit, we add the profit to the total sales value of 21 articles: Total sales value of 21 articles with profit = Total sales value of 21 articles + Profit Total sales value of 21 articles with profit = Rs.1,323 + Rs.50 = Rs.1,373.

Therefore, the total sales value of 21 articles, considering a 20% profit, is Rs.1,373.