The ground diameter of a tin chimney is 20cm, and the length is 50cm. How many square decimeters of tin is needed to make 100 such chimneys?
一节铁皮烟囱的地面直径是20cm，长是50cm，做100个这样的烟囱要铁皮多少平方分米？
<gadget id="calculator">20 / 10</gadget>
<output>2</output>

<gadget id="calculator">50 / 10</gadget>
<output>5</output>

<gadget id="calculator">3.14 * 2 * 5 * 100</gadget>
<output>3_140</output>

<result>3_140</result>