Question:
Rakesh lent out Rs 10000 for 2 years at 20% per annum, compounded annually. How much more he could earn if the interest be compounded half-yearly?
Solution:
Given:
$\mathrm{P}=\mathrm{Rs} 10,000$
$\mathrm{R}=20 \%$ p. $\mathrm{a} .$
$\mathrm{n}=2$ years
$\mathrm{A}=\mathrm{P}\left(1+\frac{\mathrm{R}}{100}\right)^{\mathrm{n}}$
$=\operatorname{Rs} 10,000\left(1+\frac{20}{100}\right)^{2}$
$=\operatorname{Rs} 10,000(1.2)^{2}$
$=\operatorname{Rs} 14,400$
When the interest is compounded half-yearly, we have:
$\mathrm{A}=\mathrm{P}\left(1+\frac{\mathrm{R}}{200}\right)^{2 \mathrm{n}}$
$=\operatorname{Rs} 10,000\left(1+\frac{20}{200}\right)^{4}$
$=\operatorname{Rs} 10,000(1.1)^{4}$
$=\operatorname{Rs} 14,641$
Difference $=$ Rs $14,641-$ Rs 14,400
$=\operatorname{Rs} 241$