To welcome the National Day, the students bought colored balls and hung them around the classroom. There are 5 colored balls on each side. How many colored balls should be hung in total?
为迎接国庆节，同学们买来彩球挂在教室四周，每边挂5个彩球，一共要挂多少个彩球？
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>