Number of millimoles of base (i.e., $\mathrm{Ca}(\mathrm{OH}{)}_2)$ $=N_1{V}_1=2\times M_1\times V_1=2\times 0.2\times 25=10$
Number of millimoles of acid (i.e., $\mathrm{HCl})={\mathrm{N}}_2{V}_2$
$$=10\times 1=10$$
As, no. of millimoles of acid $=$ no. of millimoles of base
$\therefore$ Acid is completely neutralised by base forming a neutral solution.
$\therefore \mathrm{pH}$ of the resulting solution $=7$.