1. The problem is to understand and solve questions related to commercial arithmetic, which typically involves calculations of profit, loss, discount, interest, and related concepts. 2. Important formulas include: - Profit = Selling Price (SP) - Cost Price (CP) - Loss = Cost Price (CP) - Selling Price (SP) - Profit Percentage = \frac{Profit}{Cost Price} \times 100 - Loss Percentage = \frac{Loss}{Cost Price} \times 100 - Discount = Marked Price (MP) - Selling Price (SP) - Simple Interest (SI) = \frac{P \times R \times T}{100} 3. Let's consider an example: If an article is bought for $100 and sold for $120, find the profit and profit percentage. 4. Calculate profit: $$Profit = SP - CP = 120 - 100 = 20$$ 5. Calculate profit percentage: $$Profit\% = \frac{Profit}{CP} \times 100 = \frac{20}{100} \times 100 = 20\%$$ 6. Explanation: The seller made a profit of 20 units, which is 20% of the cost price. This means the article was sold at a 20% gain. 7. Commercial arithmetic problems often require careful application of these formulas and understanding the relationship between cost price, selling price, and marked price. This example illustrates the basic approach to solving commercial arithmetic problems.