The compound interest on a certain sum for 2 years at 10\% per annum is ₹ 525. The simple interest on the same sum for double the time at half the rate percent per annum is
(a)₹ 400
(b)₹ 500
(c)₹ 600
(d)₹ 800
Answer
Answer (as printed): B
Explanation
Let the sum be ₹ $P$. Then, $\left[P\left(1+\frac{10}{100}\right)^{2}-P\right]=525$ $$\begin{aligned} & \Rightarrow P\left[\left(\frac{11}{10}\right)^{2}-1\right]=525 \\ & \Rightarrow P=\left(\frac{525 \times 100}{21}\right)=2500 . \quad \therefore \text { Sum }=₹ 2500 . \end{aligned}$$ So, S.I. $=₹\left(\frac{2500 \times 5 \times 4}{100}\right)=₹ 500$.
Explanation as extracted from the printed page; notation may be imperfect.