Find the compound interest on Rs 8000 for 9 months

$\mathrm{P}=$ Rs 8,000

$\mathrm{~T}=9$ months $=3$ quarters

$\mathrm{R}=20 \%$ per annum $=5 \%$ per quarter

$\mathrm{A}=8,000\left(1+\frac{5}{100}\right)^{3}$

$=8,000(1.05)^{3}$

$=9,261$

The required amount is Rs 9,261 .

Now,

$\mathrm{CI}=\mathrm{A}-\mathrm{P}$

$=\mathrm{Rs} 9,261-\mathrm{Rs} 8,000$

$=\mathrm{Rs} 1,261$