$$ \begin{aligned}\sqrt{20}\cdot\sqrt{5}& \xlongequal{ }\sqrt{100} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}10\end{aligned} $$ | |
① | The square root of $ 100 $ is $ 10 $. |