Given:
The rate of interest for \(1^{\text {st }} 2\) years is \(8 \%\)
For the next 3 years it is \(10 \%\)
For the period beyond 5 years it is \(12.5 \%\)
Principal \(=\operatorname{Rs} 20 \mathrm{~L}\)
Amoun paid \(=\mathrm{Rs} ~36.7 \mathrm{~L}\)
Amount \(=P+S I\)
Simple Interest, \(\mathrm{SI}=\frac{\mathrm{P} \times \mathrm{R} \times \mathrm{T}} { 100}\)
Where \(\mathrm{P} \rightarrow\) Principal, \(\mathrm{R} \rightarrow\) rate of interest, \(\mathrm{T} \rightarrow\) time
Total \(\mathrm{SI}=\mathrm{A}-\mathrm{P}=36.7 \mathrm{~L}-2 \mathrm{OL}\)
Total \(\mathrm{SI}=16.7 \mathrm{~L}\)
SI for first 2 years \(=20 \mathrm{~L} \times 2 \times \frac{8}{100}=3.2 \mathrm{~L}\)
SI for next 3 years \(=20 \mathrm{~L} \times 3 \times \frac{10}{100}=6 \mathrm{~L}\)
So, total SI for the first 5 years \(=9.2 \mathrm{~L}\)
Then, the rest of the interest is obtained at the rate of \(12.5 \%\)
Remaining interest \(=16.7 \mathrm{~L}-9.2 \mathrm{~L}=7.5 \mathrm{~L}\)
SI for next \(\mathrm{N}\) years \(=20 \mathrm{~L} \times \mathrm{N} \times 12.5 \%=7.5 \mathrm{~L}\)
\(\mathrm{N}=7.5 \mathrm{~L} \times \frac8{20} \mathrm{~L} \quad(12.5 \% \rightarrow \frac18 \mathrm{in}\) fraction \()\)
\(N=3\)
That is, total years \(=2+3+3=8\) years.