person is walking on a road at a constant speed, and a bus departs from the front and rear ends of the road at equal intervals. He found that every 15 minutes there was a bus catching up with him; every 10 minutes there was a bus passing by. How many minutes does the bus leave?
某人以匀速行走在一条公路上，公路的前后两端每隔相同的时间发一辆公共汽车．他发现每隔15分钟有一辆公共汽车追上他；每隔10分钟有一辆公共汽车迎面驶来擦身而过．问公共汽车每隔多少分钟发车一辆？
<gadget id="calculator">15 * 10</gadget>
<output>150</output>

<gadget id="calculator">10 * 15</gadget>
<output>150</output>

<gadget id="calculator">150 + 150</gadget>
<output>300</output>

<gadget id="calculator">15 + 10</gadget>
<output>25</output>

<gadget id="calculator">300 / 25</gadget>
<output>12</output>

<result>12</result>