The compound interest on a certain sum of money at 21% for 2 years is ₹11,602.5. Its simple interest (in ₹) at the same rate and for the same period is:

Given CI =  ₹ 11,602.5, T = 2 yrs , R = 21%

As we know 

CI =  $$P(1 + \frac{R}{100})^T - P$$ 

$$\Rightarrow$$ CI = $$P(1 +\frac{21}{100})^2 - P$$

$$\Rightarrow $$CI = $$P(\frac{121}{100})^2 - P$$

$$\Rightarrow$$ CI = $$P(\frac{14641}{10000}- 1)$$ 

$$\Rightarrow$$ CI = $$ P\times \frac{4641}{10000}$$

$$\Rightarrow P $$= CI $$\times \frac{10000}{4641}$$

$$\Rightarrow P $$= 11,602.5 $$\times \frac{10000}{4641}$$

$$\Rightarrow P = ₹25000 $$

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

$$\Rightarrow$$ SI = $$\frac{25000\times2\times21}{100}$$

$$\Rightarrow$$ SI = $$₹10,500$$