Simple interest on a sum for 10 years is equal to 5% of the principal. In how many years interest will be equal to the principal?

Let principal amount = Rs. $$100x$$

=> Simple interest = $$\frac{5}{100}\times100x=Rs.$$ $$5x$$

Let rate of interest = $$r\%$$ and time period = 10 years

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

=> $$\frac{100x\times r\times10}{100}=5x$$

=> $$10r=5$$

=> $$r=\frac{5}{10}=0.5\%$$

Let the interest will be equal to the principal in = $$t$$ years at 0.5% rate

=> $$\frac{100x\times 0.5\times t}{100}=100x$$

=> $$t=\frac{100}{0.5}=200$$ years

=> Ans - (C)