Question

Rajini deposited Rs 13,000 in a bank at the rate of 9 p.c.p.a. She collected Rs 1170 as interest at the end of the period. For how many years had she deposited the money?

Answer 1

Principal (P) = Rs 13,000
Rate (R) = 9 p.c.p.a.
Interest = I = Rs 1170
We have $\mathrm{I}=\frac{\mathrm{P}\times \mathrm{R}\times \mathrm{N}}{100}$
$$\begin{gathered} \Rightarrow 1170=\frac{13000\times 9\times \mathrm{N}}{100} \\ \Rightarrow 1170=130\times 9\times \mathrm{N} \end{gathered}$$

On dividing both the sides by 130, we obtain:
$$\begin{gathered} \frac{1170}{130}=\frac{130\times 9\times \mathrm{N}}{130} \\ \Rightarrow 9=9\times \mathrm{N} \end{gathered}$$
On dividing both the sides by 9, we obtain:
$$\begin{gathered} \frac{9}{9}=\frac{9\times \mathrm{N}}{9} \\ \Rightarrow 1=\mathrm{N} \\ \mathrm{Therefore},\mathrm{time}=1\mathrm{year} \end{gathered}$$