Sol. $$ \begin{aligned} & {\left[\mathrm{Ba}^{+2}\right]=\frac{25 \times 0.05}{50}=0.025 \mathrm{M}} \\ & {\left[\mathrm{~F}^{-}\right]=\frac{25 \times 0.02}{50}=0.01 \mathrm{M}} \\ & {\left[\mathrm{Ba}^{2+}\right]\left[\mathrm{F}^{-}\right]^2=25 \times 10^{-7}} \\ & \mathrm{~K}_{\mathrm{sp}}=5 \times 10^{-7}(\text { given }) \\ & \text { Ratio }=\frac{\left[\mathrm{Ba}^{+2}\right]\left[\mathrm{F}^{-}\right]^2}{\mathrm{~K}_{\mathrm{sp}}}=5 \end{aligned} $$