In how many years will a sum of ₹90 become ₹108 at \(6\displaystyle\frac{1}{4}\%\) simple interest?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \(3\frac{1}{5}\) years
Simple interest \(=\displaystyle\frac{P\times R\times T}{100}\); the interest is the growth of the sum, \(108-90=18\) rupees, and the rate is \(6\frac{1}{4}\%=\frac{25}{4}\%\).
Putting the values in the formula: \(18=\displaystyle\frac{90\times\frac{25}{4}\times T}{100}\)
The time: \(T=\displaystyle\frac{18\times100\times4}{90\times25}=\frac{7200}{2250}=3.2\)
As a mixed number, \(3.2\) years \(=3\frac{1}{5}\) years