Two brothers and sisters are playing by a circular pool with a circumference of 30 meters. They walk backwards from the same place at the same time. The elder brother walks 1.3 meters per second, and the younger sister walks 1.2 meters per second. When they met for the first time, the younger sister still had to walk How long does it take to get back to the starting point?
兄妹两人在周长为30米的圆形水池边玩，从同一地点同时背向而行，哥哥每秒走1.3米，妹妹每秒走1.2米，他们第一次相遇时，妹妹还需要走多少时间才能回到出发点？
<gadget id="calculator">30 / 1.2</gadget>
<output>25</output>

<gadget id="calculator">1.2 + 1.3</gadget>
<output>2.5</output>

<gadget id="calculator">30 / 2.5</gadget>
<output>12</output>

<gadget id="calculator">25 - 12</gadget>
<output>13</output>

<result>13</result>