Use iron sheets to make two water pipes of the same length, each section is 50dm long, and the bottom diameter is 1dm, how many square decimeters of iron sheets are needed at least?
用铁皮做2节同样长的水管，每节长50dm，底面直径是1dm，至少需要铁皮多少平方分米？
<gadget id="calculator">3.14 * 1 * 50</gadget>
<output>157</output>

<gadget id="calculator">157 * 2</gadget>
<output>314</output>

<result>314</result>