Question

For how many years should Rs. $1200$ be invested at $10\%$ p.a. in order to earn the same simple interest as is earned by investing Rs. $1800$ at $12\%$ p.a. for $5$ years ?

• A. $9$
• B. $10$
• C. $12$
• D. $11$

Answer 1

The correct option is A $9$

We have $P=\text{Rs.}1800,R=12\%$ and $T=5\text{years}$

$\Rightarrow$ $S.I=\frac{P\times R\times T}{100}$

$\Rightarrow$ $S.I=\frac{1800\times 12\times 5}{100}$

$\therefore$ $S.I=Rs.1080$

Now, we have to find $T$ with $P=\text{Rs.}1200,R=10\%$ and $S.I=\text{Rs.}1080$.

$\Rightarrow$ $S.I=\frac{P\times R\times T}{100}$

$\Rightarrow$ $1080=\frac{1200\times 10\times T}{100}$

$\Rightarrow$ $T=\frac{1080\times 100}{1200\times 10}$

$\therefore$ $T=9\text{years}$