Question

If the simple interest on a certain sum for 15 months at $7\frac{1}{2}$% per annum exceeds the simple interest on the same sum for 8 months at $12\frac{1}{2}$% per annum by Rs.32.50, then the sum (in Rs.) is

• A. Rs. 3000
• B. Rs. 3060
• C. Rs. 3120
• D. Rs. 3250

Answer 1

The correct option is C Rs. 3120

Let the sum=x Rs.
15 months=$1\frac{1}{4}=\frac{5}{4}years$
8 months=$\frac{8}{12}=\frac{2}{3}years$
Then according to the question
$\Rightarrow \frac{x\times 5\times 15}{4\times 2\times 100}-\frac{x\times 2\times 25}{3\times 2\times 100}=32.30$
$\Rightarrow \frac{75x}{800}-\frac{50x}{600}=32.50$
$\Rightarrow \frac{225x-200x}{2400}=32.50$
$\Rightarrow 25x=32.50\times 2400$
$\Rightarrow x=\frac{32.50\times 2400}{25}$
$\Rightarrow x=3120Rs$