person rides a motorcycle from home to the train station. If he travels 30 kilometers per hour, he arrives 15 minutes earlier than the train driving time. If he travels 18 kilometers per hour, he arrives 15 minutes later than the train driving time. Now this person If you plan to arrive at the train station 10 minutes before the train leaves, how fast should the person be riding the motorcycle at this time?
某人从家里骑摩托车到火车站，如果每小时行30千米，那么比火车开车时间，早到15分钟，若每小时行18千米，则比火车开车时间迟到15分钟，现在此人打算在火车开车前10分钟到达火车站，求此人此时骑摩托车的速度应该是多少？
<gadget id="calculator">15 / 60</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">30 * (1/4)</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">18 * (1/4)</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(15/2) + (9/2)</gadget>
<output>12</output>

<gadget id="calculator">30 - 18</gadget>
<output>12</output>

<gadget id="calculator">12 / 12</gadget>
<output>1</output>

<gadget id="calculator">1 + (1/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">10 / 60</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">(5/4) / (5/6)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">18 * (3/2)</gadget>
<output>27</output>

<result>27</result>