After cutting a 4-meter-long cylindrical steel into two equal sections, the sum of the surface areas of the two sections increases by 0.5 square decimeters compared to the uncut section. If the steel weighs 7.8 kilograms per cubic decimeter, the weight of one section is How many?
把一根长4米的圆柱形钢材截成相等的两段后，这两段表面积的和比未截时增加了0.5平方分米，如果每立方分米钢材重7.8千克，其中一段的重量是多少？
<gadget id="calculator">0.5 / 2</gadget>
<output>0.25</output>

<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">0.25 * 20 * 7.8</gadget>
<output>39</output>

<result>39</result>