SI = (P × R × T) ÷ 100
₹10,000 at 5% for 2 years: SI = (10,000 × 5 × 2) ÷ 100 = ₹1,000.
Simple interest is calculated only on the original principal; compound interest is calculated on principal plus previously earned interest.
Years, matching the annual rate R; convert months to a fractional year first.