Meteorologists and medical experts believe that the haze weather caused by PM2.5 fine particles is even more harmful to human health than sandstorms. The diameter of such fine particles is less than (1/20) the diameter of a human hair. The diameter of a human hair is about 0.5 mm. What is the diameter of this fine particle in mm?
气象专家和医学专家认为，由PM2.5细颗粒物造成的雾霾天气对人体健康的危害甚至比沙尘暴更大．这种细颗粒物的直径还不到人类头发丝直径的(1/20)．人类的头发丝的直径约是0.5毫米，这种细颗粒物的直径约是多少毫米．
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">0.5 * (1/20)</gadget>
<output>0.025</output>

<result>0.025</result>