A person is riding a bicycle along a bus route. A bus passes the cyclist every 3 minutes, and a bus passes the cyclist every 15 minutes. If a car departs from both ends of the station at the same interval each time, how many minutes does a car dispatch?
一个人骑车沿一条公共汽车线路行驶，每隔3分钟有一辆公共汽车迎面经过骑车人，每隔15分钟有一辆公共汽车从旁边超过骑车人．如果汽车从两端车站每次间隔同样的时间发一辆车，那么每隔多少分钟发一辆车？
<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<gadget id="calculator">3 * 15</gadget>
<output>45</output>

<gadget id="calculator">45 + 45</gadget>
<output>90</output>

<gadget id="calculator">15 + 3</gadget>
<output>18</output>

<gadget id="calculator">90 / 18</gadget>
<output>5</output>

<result>5</result>