By using the formula, find the amount and compound interest on:

Principal amount, $P=$ Rs. 10240

Rate of interest, $R=12 \frac{1}{2} \%$ p. a.

Time, $n=3$ years

The formula for the amount including the compound interest is given below :

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

$\Rightarrow A=$ Rs. $10240\left(1+\frac{25}{100 \times 2}\right)^{3}$

$\Rightarrow A=$ Rs. $10240\left(1+\frac{25}{200}\right)^{3}$

$\Rightarrow A=$ Rs. $10240\left(1+\frac{1}{8}\right)^{3}$

$\Rightarrow A=$ Rs. $10240\left(\frac{8+1}{8}\right)^{3}$

$\Rightarrow A=$ Rs. $10240\left(\frac{9}{8}\right)^{3}$

$\Rightarrow A=$ Rs. $10240(1.125 \times 1.125 \times 1.125)^{3}$

$\Rightarrow A=$ Rs. 14580

i. e., the amount including the compound interest is Rs 14580 .

$\therefore$ Compound interest $=$ Rs $(14580-10240)=$ Rs. 4340