The circumference of a circular flowerbed is 30 meters long, and a red flag is inserted every 3 meters along the periphery, and two yellow flags are inserted in the middle of every two red flags. How many yellow flags are planted around the flower garden?
一个圆形花圃周围长30米，沿周围每隔3米插一面红旗，每两面红旗中间插两面黄旗．花圃周围共插了多少面黄旗？
<gadget id="calculator">30 / 3</gadget>
<output>10</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<result>20</result>