 Hello and welcome to the session. In this session we discussed the following question which says the selling price of 10 articles is equal to the cost price of 12 articles by in the gain percent. Before we move on to the solution, let's discuss the formula for gain. Gain is equal to the selling price that is SP minus the cost price that is CP and gain percent is equal to gain upon the cost price CP into 100 percent. This is the key idea. To be used in this question. Let's proceed with the solution now. We take let the selling price or say SP of one article be equal to rupee 1. So the selling price or SP of 12 articles would be equal to rupees 12 and also SP that is the selling price of 10 articles would be equal to rupees 10. Now according to the question we have that the cost price of 12 articles is equal to the selling price of 10 articles that is cost price of 12 articles equal to selling price SP of 10 articles and we know that SP of 10 articles or the selling price of 10 articles is rupees 10. So this is equal to rupees 10. So we get cost price of 12 articles is equal to rupees 10. Now the selling price of 12 articles is rupees 12 and cost price of 12 articles is rupees 10. So we see that SP of 12 articles is more than CP of 12 articles. Therefore there is a gain and this gain is equal to the selling price of 12 articles minus the cost price of 12 articles. So this is equal to rupees 12 minus rupees 10 equal to rupees 2. So gain is equal to rupees 2. Now let's find out the gain percent. This is equal to gain that is 2 upon the cost price which is 10 into 100 percent. So this 0 cancels with this 0 and this is equal to 20 percent. Thus we get gain percent is equal to 20 percent. So 20 percent is our final answer. This completes the session. Hope you have understood the solution for this question.