A cylindrical ventilation pipe is 15 meters long and has a cross-sectional radius of 10 cm. How many square meters of iron sheet is needed to produce a ventilation pipe of this type?
一种圆柱形通风管，长15米，横截面口半径是10厘米，生产一个这种通风管需铁皮多少平方米．
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">2 * 3.14 * (1/10) * 15</gadget>
<output>9.42</output>

<result>9.42</result>