A cylindrical steel is 12 meters long. If it is cut into three equal sections (the section is parallel to the bottom surface), its surface area will increase by 18 square decimeters. If the steel weighs 7.8 kilograms per cubic decimeter, the original weight of this steel is How many kilograms.
一根圆柱形钢材长12米，如果将它截成相等的三段(截面与底面平行)，它的表面积就增加18平方分米，如果每立方分米钢重7.8千克，这根钢材原来重多少千克．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">18 / 4</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">12 * 10</gadget>
<output>120</output>

<gadget id="calculator">(9/2) * 120 * 7.8</gadget>
<output>4_212</output>

<result>4_212</result>