Q.Find the simple interest on ₹6,000 at 8% per annum for 3 years, and the amount payable at the end of the period.

Simple interest charges interest only on the original principal: $\text{SI}=\tfrac{Prn}{100}$, amount $=P\left(1+\tfrac{rn}{100}\right)$. Compound interest adds each period's interest to the principal, so amount $=P\left(1+\tfrac{r}{100}\right)^{n}$ (annual compounding) and $\text{CI}=\text{Amount}-P$. …