Two toy airplanes start from the same place on the same circle and fly in opposite directions at a constant speed. One of them takes 15 seconds to fly a circle, and the other takes 30 seconds to fly a circle. Then from the time they meet for the first time How many seconds will it take for the second encounter.
两架玩具飞机在同一个圆周上从同一地点出发向相反方向作匀速圆周飞行，其中一架飞机飞一圈需15秒，另一架飞一圈需30秒，那么从它们第一次相遇到第二次相遇需要多少秒．
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/15) + (1/30)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / (1/10)</gadget>
<output>10</output>

<result>10</result>