| $$ \begin{aligned}\frac{720}{3240}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}} \frac{ 720 : \color{orangered}{ 360 } }{ 3240 : \color{orangered}{ 360 }} \xlongequal{ } \\[1 em] & \xlongequal{ }\frac{2}{9}\end{aligned} $$ | |
| ① | Divide both the top and bottom numbers by $ \color{orangered}{ 360 } $. |