A cylindrical piece of steel is 20 decimeters long and has a base radius of 5 decimeters. If the steel weighs 7.8 kilograms per cubic decimeter, how many kilograms does this piece of steel weigh?
一根圆柱形钢材，长20分米，底面半径是5分米，若每立方分米钢重7.8千克，这根钢材重多少千克？
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25 * 20 * 7.8</gadget>
<output>12_246</output>

<result>12_246</result>