Simple interest on a sum for 5 years is equal to 20% of the principal. In how many years interest will be equal to the principal?

Let principal amount = Rs. $$100x$$

=> Simple interest = $$\frac{20}{100}\times100x=Rs.$$ $$20x$$

Let rate of interest = $$r\%$$ and time period = 5 years

=> Simple interest = $$\frac{P\times R\times T}{100}$$

=> $$\frac{100x\times r\times5}{100}=20x$$

=> $$r=\frac{20}{5}=4\%$$

Let the interest will be equal to the principal in = $$t$$ years at 4% rate

=> $$\frac{100x\times 4\times t}{100}=100x$$

=> $$t=\frac{100}{4}=25$$ years

=> Ans - (B)