There is a downpipe that is 3 meters long and whose cross-section is a square with a side length of 1 decimeter. How many square decimeters of iron sheets are needed to make 10 such downpipes?
有一种落水管道，长3米，横截面是边长为1分米的正方形．制作10根这样的落水管道，共需多少平方分米的铁皮？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 4 * 3 * 10 * 100</gadget>
<output>1_200</output>

<result>1_200</result>