Find the amount of Rs 4096 for 18 months at

Given:

$\mathrm{P}=\mathrm{Rs} 4,096$

$\mathrm{R}=12.5 \%$ p. a.

$\mathrm{n}=18$ months $=1.5$ years

We have :

$\mathrm{A}=\mathrm{P}\left(1+\frac{\mathrm{R}}{100}\right)^{\mathrm{n}}$

When the interest is compounded semi-annually, we have:

$\mathrm{A}=\mathrm{P}\left(1+\frac{\mathrm{R}}{200}\right)^{2 \mathrm{n}}$

$=\operatorname{Rs} 4,096\left(1+\frac{12.5}{200}\right)^{3}$

$=\operatorname{Rs} 4,096(1.0625)^{3}$

$=\operatorname{Rs} 4,913$

Thus, the required amount is Rs $4,913 .$