Solution

Given:

Present value $$= \text{Rs}\ 10240$$
Interest rate$$= 12\dfrac{1}{2} \%$$ per annum $$= \dfrac{25}{2} \%$$
Time $$=3$$ years

To find the amount we have the formula,

Amount $$(A) = P\left(1+\dfrac{r}{100}\right)^n$$
where, $$P$$ is present value, $$r$$ is rate of interest, $$n$$ is time in years.

Now substituting the values in above formula we get,

$$\therefore A = 10240\left(1+\dfrac{25}{200}\right)^3$$

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

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

$$\Rightarrow A = 10240 × \dfrac{729}{512} = 20 × 729$$

$$\Rightarrow A = \text{Rs } 14580$$


And, Compound interest $$= A – P$$

$$= 14580 – 10240= \text{Rs}\ 4340$$