Ishita invested a sum of Rs 12000 at 5% per annum compound interest.

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

$13,230=12,000\left(1+\frac{5}{100}\right)^{\mathrm{n}}$

$(1.05)^{\mathrm{n}}=\frac{13,230}{12,000}$

$(1.05)^{\mathrm{n}}=1.1025$

$(1.05)^{\mathrm{n}}=(1.05)^{2}$

On comparing both the sides, we get:

n = 2

Thus, the value of $\mathrm{n}$ is two years.