The list price (marked price) of an article is Rs. 900. It is sold after allowing two successive discounts of 20% and 10%. What is the final selling price of the article in rupees?

Introduction / Context:
This question is another example of successive discounts on a marked price. A discount is applied, and then another discount is applied on the already reduced price. We must compute the final selling price starting from the marked price of Rs. 900. It illustrates how multiple discounts combine multiplicatively rather than additively.

Given Data / Assumptions:
- Marked price (MP) of the article = Rs. 900.
- First discount = 20 percent on MP.
- Second discount = 10 percent on the price after the first discount.
- We must find the final selling price in rupees.

Concept / Approach:
Each discount reduces the current price by a certain percentage. A 20 percent discount corresponds to multiplying the price by 0.80. A 10 percent discount corresponds to multiplying the current price by 0.90. The final selling price is MP multiplied by both discount factors. It is important not to add the percentages directly (20 + 10) since the second discount is applied to a smaller base price.

Step-by-Step Solution:
Marked price MP = Rs. 900. First discount 20% gives factor = 1 - 20 / 100 = 0.80. Price after first discount = 900 * 0.80 = Rs. 720. Second discount 10% gives factor = 1 - 10 / 100 = 0.90. Final selling price = price after first discount * 0.90 = 720 * 0.90. Compute 720 * 0.90 = Rs. 648.

Verification / Alternative check:
We can also compute directly from the marked price: final factor = 0.80 * 0.90 = 0.72. Then selling price = 900 * 0.72 = 648. This matches the previous calculation, confirming that the final selling price is Rs. 648.

Why Other Options Are Wrong:
640 and 700: These amounts do not correspond to any simple factor from 900 after two correct discounts of 20% and 10%.
720: This is the price after only the first 20% discount, before the 10% discount is applied.
738: This might arise from an incorrect multiplication or from applying one discount incorrectly.

Common Pitfalls:
One common mistake is to add discounts and take a single discount of 30%, which would give 900 * 0.70 = 630, not matching any option. Another error is to apply the second discount on the original price instead of the already discounted price. Always remember that successive discounts act one after another, each on the current reduced price.

Final Answer:
The final selling price of the article after two successive discounts is Rs. 648.