In how many years the compound interest on Rs. 10,000 at the rate of 10% will be Rs. 2,100?

2 Years

The Formula that we used here is -

Amount = P$(1 \;+\; \frac{R}{100})^t$

and Amount = Principal + Compound Interest

⇒ 10000 + 2100 = 10000 $(1 \;+\; \frac{10}{100})^t$

⇒ 12100 = 10000 $(1 \;+\; \frac{1}{10})^t$

⇒ (\(\frac{11}{100}\))² = $( \frac{1}{10})^t$

So, t = 2

Hence, time take is 2 years.