If $$x = {\left( {0.25} \right)^{\frac{1}{2}}},$$   $$y = {\left( {0.4} \right)^2},$$   $$z = {\left( {0.216} \right)^{\frac{1}{2}}}$$   then-

$$\eqalign{ & x = {\left( {0.25} \right)^{\frac{1}{2}}} \cr & x = \root 2 \of {0.25} = 0.5{\text{ }} \cr & y = {\left( {0.4} \right)^2} \cr & y = 0.16 \cr & z = {\left( {0.216} \right)^{\frac{1}{2}}} \cr & z = \root 2 \of {0.216} = 0.464 \cr & \therefore x > z > y \cr} $$