The two brothers and sisters set off from home to go to school at the same time. The elder brother walks 90 meters per minute, and the younger sister walks 60 meters per minute. When the elder brother arrives at the school gate, he finds that he forgot to bring his textbooks, and immediately goes home to pick them up along the same road. When he meets his younger sister at 180 meters away from the school, how far away is their home from the school? ?
兄妹二人同时由家里出发去上学．哥哥每分钟走90米，妹妹每分钟走60米，哥哥到校门时发现忘带课本，立即沿原路回家去取，行至离校180米处和妹妹相遇，则他们家离校多少米？
<gadget id="calculator">90 - 60</gadget>
<output>30</output>

<gadget id="calculator">2 / 30</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">180 * (1/15)</gadget>
<output>12</output>

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

<gadget id="calculator">720 + 180</gadget>
<output>900</output>

<result>900</result>