A section of cylindrical steel is 5 meters long and is cross-sectioned into two small cylinders with an increased surface area of 20 square centimeters. If the steel weighs 7.8 grams per cubic centimeter, how many kilograms does this piece of steel weigh? (retain the whole kilogram)
一段圆柱形钢材长5米，横截成两个小圆柱表面积增加了20平方厘米．如果每立方厘米钢重7.8克，这段钢材重多少千克？(得数保留整千克)
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">7.8 / 1_000</gadget>
<output>0.0078</output>

<gadget id="calculator">10 * 5 * 100 * 0.0078</gadget>
<output>39</output>

<result>39</result>