It takes 30 minutes for the father to go from home to the factory, and 20 minutes for the son. One day, the father walked 5 minutes earlier than the son, how many minutes did the son catch up with the father?
父亲从家到工厂需要30分钟，儿子需要20分钟．一天，父亲比儿子早走5分钟，儿子几分钟追上父亲？
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/30) * 5</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) - (1/30)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/6) / (1/60)</gadget>
<output>10</output>

<result>10</result>