Kamala borrowed from Ratan a certain sum at a certain rate for two years simple interest.

Let the sum be Rs P and the rate of interest be R\%.

We know that Kamla paid Rs 200 as simple interest.

$\therefore 200=\frac{\operatorname{PR}(2)}{100}$

$\mathrm{PR}=10,000 \quad \ldots(1)$

Also, Kamla received Rs 210 as compound interest.

$\therefore 210=\mathrm{P}\left(1+\frac{\mathrm{R}}{100}\right)^{2}-1$

$210(10,000)=\mathrm{P}\left(\mathrm{R}^{2}+200 \mathrm{R}\right)$

$210 \mathrm{R}=\mathrm{R}^{2}+200 \mathrm{R} \quad[$ from $(1)]$

$\mathrm{R}=10 \%$ p. $\mathrm{a}$

Putting the equation in $(1)$, we get:

$\mathrm{P}=1,000$

Thus, the required sum is Rs 1,000 and the rate of interest is $10 \%$