The simple interest as a sum of money is $\frac{4}{5}$ of the principal. Find the rate of Simple interest if both the rate of interest and time are numerically equal.
Answer & explanation
Correct answer: option 4
S.I. = $\frac{4}{5}$ of the Principal
P : S.I. = 5 : 4
S.I. = \(\frac{P\;R\;T}{100}\)
4 = \(\frac{5\;R\;T}{100}\)
R× T = 80
Here R = T (given), therefore,
R2 = 80
R = 4 \(\sqrt {5}\)