Explanation: To solve this problem, we need to understand the concept of discounts and how to apply them to a given price. The problem states that 2 plates of aloo ke gutke are served at Rs 600. Therefore, the cost of one plate without any discount is:
\[
\text{Cost per plate} = \frac{\text{Total cost for 2 plates}}{2} = \frac{600}{2} = 300 \text{ rupees}
\]
Next, we need to apply a 20% discount to the cost of one plate. The discount amount can be calculated as:
\[
\text{Discount amount} = \text{Cost per plate} \times \left(\frac{\text{Discount percentage}}{100}\right) = 300 \times \left(\frac{20}{100}\right) = 300 \times 0.20 = 60 \text{ rupees}
\]
The final price after applying the discount is:
\[
\text{Final price} = \text{Cost per plate} - \text{Discount amount} = 300 - 60 = 240 \text{ rupees}
\]
Therefore, the person should pay Rs 240 for one plate of aloo ke gutke with a 20% discount.
This problem tests the student's ability to calculate the cost per unit and apply a percentage discount correctly. It is important to first determine the cost per unit before applying the discount, as applying the discount to the total cost for multiple units would lead to an incorrect result. Additionally, understanding the concept of percentage and how to convert it into a decimal for calculation is crucial in solving such problems.