The compound interest on Rs 16000 for 9 months at 20% per annum, interest being compounded quarterly, is = ?

Answer: Option C

The interest is compounded quarterly,
$$\therefore R=\frac{20}{4}=5\%$$
Time = 3 quarters
$$\begin{array}{rl}& \therefore C.I.=P\left[{\left(1+\frac{R}{100}\right)}^T-1\right]\\ & =16000\left[{\left(1+\frac{5}{100}\right)}^3-1\right]\\ & =16000\left[{\left(\frac{21}{20}\right)}^3-1\right]\\ & =16000\left(\frac{9261-8000}{8000}\right)\\ & =16000\times \frac{1261}{8000}\\ & =\text{Rs}\text{.}2522\end{array}$$