Simple Interest — Deferred balance with SI on the remainder: A music system costs ₹ 8000. A buyer pays ₹ 3500 now and the balance after 18 months with simple interest at 8% p.a. Find the total amount paid.

Introduction / Context:
When a balance is carried forward with simple interest, the interest accrues only on the unpaid remainder for the specified time. The total outlay is the upfront payment plus the future payment including its interest.

Given Data / Assumptions:

• Cash price = ₹ 8000
• Paid now = ₹ 3500 → balance principal = ₹ 4500
• Interest on balance: r = 8% p.a.; t = 18 months = 1.5 years

Concept / Approach:
Interest on balance = 4500 * 0.08 * 1.5. Total paid = 3500 + 4500 + interest.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

• Other totals imply incorrect interest on the balance or wrong time conversion.

Common Pitfalls:

• Treating 18 months as 18 years or forgetting to convert to 1.5 years.

Final Answer:
₹ 8540.