| $$ \begin{aligned}5\sqrt{6}\cdot2\sqrt{3}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}30\sqrt{2}\end{aligned} $$ | |
| ① | $$ 10 \sqrt{18} =
10 \sqrt{ 3 ^2 \cdot 2 } =
10 \sqrt{ 3 ^2 } \, \sqrt{ 2 } =
10 \cdot 3 \sqrt{ 2 } =
30 \sqrt{ 2 } $$ |