A sum of money at compound interest amounts to $\text{Rs. }650$ at the end of the first year and $\text{Rs. }676$ at the end of the second year. The sum of money is:

Let the initial principal amount be $P$ and the annual interest rate be $R\%$.
According to the formula for compound interest:

* Amount at the end of Year 1:

$$P\left(1+\frac{R}{100}\right)=650\text{— (Equation 1)}$$

* Amount at the end of Year 2:

$$P{\left(1+\frac{R}{100}\right)}^2=676\text{— (Equation 2)}$$

Divide Equation 2 by Equation 1 to find the multiplier factor:

$$\frac{P{\left(1+\frac{R}{100}\right)}^2}{P\left(1+\frac{R}{100}\right)}=\frac{676}{650}$$

$$1+\frac{R}{100}=\frac{26}{25}$$

Substitute this multiplier factor value back into Equation 1:

$$P\times \left(\frac{26}{25}\right)=650$$

$$P=650\times \frac{25}{26}$$

$$P=25\times 25=\text{Rs. }625$$