How many square decimeters of iron sheet are needed to make a cylindrical iron drum with a height of 3 decimeters and a bottom diameter of 4 decimeters?
做一个圆柱形无盖铁桶，高3分米，底面直径4分米，需要铁皮多少平方分米？
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">3.14 * 4 * 3</gadget>
<output>37.68</output>

<gadget id="calculator">12.56 + 37.68</gadget>
<output>50.24</output>

<result>50.24</result>