Simple Interest — For a principal of ₹ 1500, the simple interest is ₹ 30 in 4 years and ₹ 60 in 8 years. Find the annual rate of simple interest.

Introduction / Context:
The proportionality of simple interest to time lets us infer the rate from any correct time-interest pair.

Given Data / Assumptions:

• P = ₹ 1500.
• SI in 4 years = ₹ 30.
• SI in 8 years = ₹ 60 (consistent with linearity).

Concept / Approach:
SI = P * r * t ⇒ r = SI / (P * t).

Step-by-Step Solution:
Using the 4-year data: r = 30 / (1500 * 4) = 30 / 6000 = 0.005.Convert to percent: 0.5% per annum.

Verification / Alternative check:
Using 8-year data: r = 60 / (1500 * 8) = 60 / 12000 = 0.005 = 0.5%.

Why Other Options Are Wrong:
2.5%, 1.5%, 1%, 0.25% do not produce the given SI pairs.

Common Pitfalls:
Forgetting to divide the percent by 100 when converting to decimal for formulas.

Final Answer:
0.5%