Let's break down the problem step by step.

Step 1: Calculate the new marked price after a 20% increase.

The original marked price of the plasma TV is Rs. 63,000.

To increase the marked price by 20%: $\text{New Marked Price} = 63,000 + (63,000 \times 0.20) = 63,000 + 12,600 = 75,600 \text{ Rs.}$

Step 2: Apply a 20% discount to the new marked price.

Now, a 20% discount is offered on the new marked price of Rs. 75,600.

To calculate the selling price after the discount: $\text{Selling Price} = 75,600 - (75,600 \times 0.20) = 75,600 - 15,120 = 60,480 \text{ Rs.}$

Step 3: Calculate the percentage change in the selling price.

The original marked price was Rs. 63,000, so the original selling price was Rs. 63,000 (since no discounts or price increases were mentioned before).

The percentage change in the selling price is calculated as: $\text{Percentage Change} = \frac{\text{New Selling Price} - \text{Original Marked Price}}{\text{Original Marked Price}} \times 100$ $\text{Percentage Change} = \frac{60,480 - 63,000}{63,000} \times 100 = \frac{-2,520}{63,000} \times 100 \approx -4\%$

Final Answer:

The percentage change in their selling price is a decrease of approximately 4%.

Would you like more details, or do you have any questions about this? Here are some related questions you might find useful:

1. What would be the final selling price if the discount offered was 25% instead of 20%?
2. How does increasing the marked price by a different percentage affect the final selling price after applying the same discount?
3. What would be the impact on the percentage change in selling price if no discount was offered?
4. How do we calculate the net effect of successive percentage changes (like a price increase followed by a discount)?
5. How can VJ Sales determine the optimal discount percentage to maximize profit?

Tip: When dealing with successive percentage changes (like a markup followed by a discount), remember that the changes are applied successively, not cumulatively, which can result in a net decrease even when both percentages are the same.