After two 3-meter-long cylinders with the same base area are put together to form a steel cylinder, the surface area is reduced by 1.2 square decimeters. If the steel weighs 7.8 kilograms per cubic decimeter, how many kilograms does the assembled steel weigh?
把两根底面积相等的3米长的圆柱体拼成一根圆柱体钢材以后，表面积减少了1.2平方分米，如果每立方分米钢材重7.8千克，拼成后的这根钢材重多少千克？
<gadget id="calculator">1.2 / 2</gadget>
<output>0.6</output>

<gadget id="calculator">0.6 * 3 * 10 * 2 * 7.8</gadget>
<output>280.8</output>

<result>280.8</result>