Simple Interest — What is the simple interest on ₹ 4000 at 12.5% per annum from 4 February 2005 to 18 April 2005?

Introduction / Context:
Date-based simple interest questions require converting the exact period into a fraction of a year and then applying SI = P * r * t.

Given Data / Assumptions:

• P = ₹ 4000.
• r = 12.5% per annum = 0.125.
• From 4 Feb 2005 to 18 Apr 2005.
• Use a 365-day year for t.

Concept / Approach:
Compute number of days between dates, convert to years t = days / 365, then SI = P * r * t.

Step-by-Step Solution:
Days from 2005-02-04 to 2005-04-18 = 73 days.t = 73 / 365 = 0.2 years exactly.SI = 4000 * 0.125 * 0.2 = 4000 * 0.025 = ₹ 100.

Verification / Alternative check:
12.5% per year implies 1/8 of principal each year. For 0.2 years, take 1/5 of 1/8 of P: (P / 8) / 5 = P / 40 = 4000 / 40 = 100.

Why Other Options Are Wrong:
₹ 120, ₹ 150, ₹ 200, ₹ 215 correspond to incorrect day counts or wrong fractions of a year.

Common Pitfalls:
Using 360-day convention without being told; miscounting inclusive/exclusive dates. The 73-day difference gives an exact 0.2 year.

Final Answer:
₹ 100