Three cars, slow, medium, and fast, start from the same place at the same time and chase a cyclist in front along the same road. The speeds of these three cars are 10 kilometers, 15 kilometers, and 25 kilometers per hour respectively. It is known that the slow train and the medium train take 20 hours and 10 hours to catch up with the cyclist respectively, so how many hours does it take for the fast train to catch up with the cyclist?
慢、中、快三辆车同时从同地出发，沿同一条公路追赶前面一个骑车人，这三辆车速度分别是每小时10千米、15千米、25千米．已知慢车、中车分别用20小时、10小时追上骑车人，那么快车追上骑车人用了多少小时．
<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<gadget id="calculator">25 - 5</gadget>
<output>20</output>

<gadget id="calculator">100 / 20</gadget>
<output>5</output>

<result>5</result>