If 21% of an electricity bill is given as a discount,\nand the remaining amount to be paid is Rs. 1817, what was the original electricity bill before the discount was applied?

Introduction / Context:
This is a classic reverse percentage question involving a discount on an electricity bill. Instead of asking for the discount itself, the problem gives the discounted payable amount and the discount rate, and asks for the original bill value. Such questions help build confidence in working backward from percentage based changes in billing and commerce situations.

Given Data / Assumptions:

• Discount on the electricity bill = 21% of the original bill.
• Amount still to be paid after discount = Rs. 1817.
• The remaining amount represents the portion of the bill after discount.
• No additional charges or taxes are mentioned, so we ignore them.

Concept / Approach:
If a discount of d% is given on a bill, then the customer pays (100 - d)% of the original amount. Here, the customer pays 79% of the original bill, because 100% - 21% = 79%. The key idea is to interpret Rs. 1817 as 79% of the original bill. We use a simple proportion equation original * 79 / 100 = 1817, and then solve for the original bill using division.

Step-by-Step Solution:
Step 1: Let the original bill amount be B rupees.Step 2: Discount is 21% of B, so payable amount = 79% of B.Step 3: Write the relationship as an equation: 0.79 * B = 1817.Step 4: Solve for B: B = 1817 / 0.79.Step 5: Compute the value: B = 2300 rupees, so the original bill was Rs. 2300.

Verification / Alternative check:
To verify, calculate 21% of Rs. 2300. That gives 2300 * 21 / 100 = 2300 * 0.21 = 483 rupees. Subtract this discount from the original bill: 2300 - 483 = 1817 rupees. This matches the amount stated in the question, so our calculation is confirmed.

Why Other Options Are Wrong:
Rs. 1502, Rs. 1538 and Rs. 1817 are all less than the payable amount plus discount, so they cannot lead to a payable amount of Rs. 1817 after a 21% reduction.
Rs. 2336 would give a payable amount of 79% of 2336, which is 1845.44 rupees, not 1817 rupees, so it is also incorrect.

Common Pitfalls:
A common mistake is to treat Rs. 1817 as 21% of the bill rather than the remaining 79%, which leads to a very large and incorrect original amount. Another typical error is to subtract 21% of 1817, which is conceptually wrong because the discount applies to the original bill, not to the already discounted amount. Always identify clearly whether the given amount corresponds to the original total, the discounted price, the discount itself, or the remaining part of the quantity.

Final Answer:
The original electricity bill amount was Rs. 2300.