A piece of round steel has a cross-sectional diameter of 20 cm and a length of 2 meters. If the mass of steel per cubic centimeter is 7.8 grams, then how many kilograms is the mass of this round steel? (retain one decimal place)
一根圆钢，截面直径是20厘米，长2米，如果每立方厘米钢的质量是7.8克，那么这根圆钢的质量约是多少千克？(得数保留一位小数)
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">2 * 100</gadget>
<output>200</output>

<gadget id="calculator">3.14 * 100 * 200 * 7.8</gadget>
<output>489_840</output>

<result>489_840</result>