Question

The compound interest on a certain sum for $2$ years at $10$% per annum is $Rs.525$. The simple interest on the same sum for double the time at half the rate percent per annum is:

• A. $Rs.400$
• B. $Rs.500$
• C. $Rs.600$
• D. $Rs.800$

Answer 1

The correct option is B $Rs.500$

Let the sum be $Rs.P$.
Then, $[P{(1+\frac{10}{100})}^2-P]=525$
$\Rightarrow P[{\left(\frac{11}{10}\right)}^2-1]=525$
$\Rightarrow P=\left(\frac{525\times 100}{21}\right)=2500$.
$\therefore Sum=Rs.2500$.
So, $S.I.=Rs.\left(\frac{2500\times 5\times 4}{100}\right)=Rs.500$