Cut off a section of cylindrical steel with a diameter of 20cm, and forge it into a conical part with a bottom diameter of 40cm and a height of 12cm. How long should the steel be cut?
把直径为20cm的圆柱形钢材截下一段，锻造成底面直径40cm，高12cm的圆锥形零件，求要截下多长的钢材？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

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

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<gadget id="calculator">12 / 314</gadget>
<output>6/157 = around 0.038217</output>

<gadget id="calculator">(1/3) * 3.14 * 400 * (6/157)</gadget>
<output>16</output>

<result>16</result>