A cylindrical iron ventilation pipe, 5 meters long and 10 cm in diameter at the bottom. How many square decimeters of iron sheets are needed to make such a section of ventilation pipe at least?
一节圆柱形铁皮通风管，长5米，底面直径10厘米．做这样一节通风管至少需要用铁皮多少平方分米？
<gadget id="calculator">10 / 10</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 1 * 5 * 10</gadget>
<output>157</output>

<result>157</result>