A dealer sells a machine whose marked price is Rs. 3,840 at a discount of 20 percent on the marked price. What is the selling price of the machine after this discount?

Introduction / Context:
This is a direct application of percentage discount on a marked price. Such questions are basic but very common in the profit and loss section of aptitude tests and also occur frequently in everyday shopping situations.

Given Data / Assumptions:

• Marked price of the machine = Rs. 3,840.
• Discount rate = 20 percent on the marked price.
• Selling price equals marked price minus discount amount.

Concept / Approach:
A discount of 20 percent means the buyer pays 80 percent of the marked price. Instead of first calculating the discount and then subtracting, it is often quicker to directly compute 80 percent of the marked price. Mathematically, selling price S = (100 − discount percent) / 100 * marked price.

Step-by-Step Solution:
Step 1: Discount percent = 20 percent, so payable percent = 100 − 20 = 80 percent. Step 2: Selling price S = (80 / 100) * 3,840. Step 3: Simplify 80 / 100 to 4 / 5. Step 4: Compute S = (4 / 5) * 3,840. Step 5: First find 3,840 / 5 = 768, then multiply by 4 to get 3,072. Step 6: Thus, the selling price is Rs. 3,072.

Verification / Alternative check:
We can also compute the discount directly. Discount amount = 20 percent of 3,840 = (20 / 100) * 3,840 = 768. Subtract this from the marked price: 3,840 − 768 = 3,072. This matches the previous calculation and confirms the answer.

Why Other Options Are Wrong:

• 3,500 implies a much smaller discount than 20 percent.
• 4,608 would actually be greater than the marked price, which is not possible after giving a discount.
• 3,240 corresponds to a different discount percentage, not exactly 20 percent.

Common Pitfalls:
Some learners mistakenly add the discount to the marked price or confuse discount percentage with the percentage to be paid. Always remember that a discount reduces the price and that the selling price is the remaining fraction of the marked price after the discount is subtracted.

Final Answer:
The selling price of the machine is Rs. 3,072.