Find the compound interest at the rate of 5% per annum for 3 years

We know that:

$P=\frac{S I \times 100}{R T}$

$\therefore \mathrm{P}=\frac{1200 \times 100}{5 \times 3}$

= 8,000

Now,

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

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

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

$=9,261$

Now,

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

$=9,261-8,000$

$=1,261$

Thus, the required compound interest is Rs 1,261 .