Roll a cylindrical ventilation pipe with a thin iron sheet. The length of the pipe is 12 meters and the radius is 1 decimeter. How many square meters of iron sheet are needed?
用薄铁皮卷一个圆柱形的通风管，管长12米，半径1分米，需要多少平方米铁皮？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">3.14 * (1/10) * 2 * 12</gadget>
<output>7.536</output>

<result>7.536</result>