The two sisters went from home to the Children's Palace at the same time, with a total length of 770 meters. The younger sister walks 60 meters per minute, and the older sister rides a bicycle at a speed of 160 meters per minute to the Children's Palace and returns immediately, and meets her sister on the way. At this time, how many minutes did my sister leave?
姐妹俩同时从家里到少年宫，路程全长770米．妹妹步行每分钟行60米，姐姐骑自行车以每分钟160米的速度到达少年宫后立即返回，途中与妹妹相遇．这时妹妹走了几分钟？
<gadget id="calculator">60 + 160</gadget>
<output>220</output>

<gadget id="calculator">2 / 220</gadget>
<output>1/110 = around 0.009091</output>

<gadget id="calculator">770 * (1/110)</gadget>
<output>7</output>

<result>7</result>