Two brothers and sisters walk from point A to point B at the same time. The elder brother walks 180 meters per minute, and the younger sister walks 60 meters per minute. The elder brother walks to B and returns immediately. The distance between AB and AB is 1440 meters. How many meters did the younger sister walk when the two met?
兄妹两人同时从A地向B地走去，哥哥每分钟行180米，妹妹每分钟行60米，哥哥行到B地立即返回．AB两地相距1440米．两人相遇时，妹妹行了多少米？
<gadget id="calculator">180 + 60</gadget>
<output>240</output>

<gadget id="calculator">2 / 240</gadget>
<output>1/120 = around 0.008333</output>

<gadget id="calculator">1_440 * (1/120)</gadget>
<output>12</output>

<gadget id="calculator">60 * 12</gadget>
<output>720</output>

<result>720</result>