Cut a cylindrical steel bar into two planar cylindrical steel bars along the diameter of its bottom surface, the cut surface is exactly a square with a perimeter of 16dm. If steel weighs 7.8kg per cubic decimeter, how many kilograms does the original steel weigh?
把一根圆柱形钢材沿着它的底面直径切成两根平面圆柱形钢材，切面正好是周长为16dm的正方形．若每立方分米钢重7.8kg，求原钢材重多少千克？
<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4 * 4</gadget>
<output>50.24</output>

<gadget id="calculator">7.8 * 50.24</gadget>
<output>391.872</output>

<result>391.872</result>