cylindrical iron sheet bucket without a cover is 12 decimeters high and the bottom diameter is 20 decimeters high. How many square decimeters of iron sheet should be used to make this bucket?
一个无盖的圆柱形铁皮水桶，高为12分米，底面直径是高的20分米，做这个水桶，至少用铁皮多少平方分米？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<gadget id="calculator">3.14 * 20 * 12</gadget>
<output>753.6</output>

<gadget id="calculator">314 + 753.6</gadget>
<output>1_067.6</output>

<result>1_067.6</result>