The circumference of a circular pool is 100 meters. Plant a willow tree every 5 meters by the pool, hang 5 lights on each willow tree, how many lights will be hung in total.
一个圆形水池的周长是100米．在水池边上每隔5米种一棵柳树，每棵柳树上挂5盏灯，一共要挂多少盏灯．
<gadget id="calculator">100 / 5</gadget>
<output>20</output>

<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<result>100</result>