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 10 seconds to fly a circle, and the other takes 25 seconds to fly a circle. How many seconds will it take for the third 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做匀速圆周飞行，其中一架飞机飞一圈需10秒，另一架飞一圈需要25秒，那么从他们第一次相遇到第三次相遇需要多少秒．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 25</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">(1/10) + (1/25)</gadget>
<output>7/50 = around 0.14</output>

<gadget id="calculator">2 / (7/50)</gadget>
<output>100/7 = around 14.285714</output>

<result>100/7 = around 14.285714</result>