Simple interest on ₹ 500 for 4 years at 6.25\% per annum is equal to the simple interest on ₹ 400 at 5\% per annum for a certain period of time. The period of time is
(a)4 years
(b)5 years
(c)$6 \frac{1}{4}$ years
(d)$8 \frac{2}{3}$ years
Answer
Answer (as printed): C
Explanation
Let the required time be $T$ years. Then, $\frac{500 \times 6.25 \times 4}{100}=\frac{400 \times 5 \times T}{100}$ $$\Rightarrow \quad T=\left(\frac{500 \times 6.25 \times 4}{400 \times 5}\right) \mathrm{yrs}=6 \frac{1}{4} \mathrm{yrs} .$$
Explanation as extracted from the printed page; notation may be imperfect.