A 2-meter-long cylindrical wood with a radius of 10 cm in cross-section is cut vertically along the diameter of the cross-section and divided into two equal pieces.
一根2米长的圆柱形木料，横截面的半径是10厘米，沿横截面的直径垂直锯开，分成相等的两块，表面积比原来增加多少平方厘米．
<gadget id="calculator">2 * 100</gadget>
<output>200</output>

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

<gadget id="calculator">200 * 20</gadget>
<output>4_000</output>

<result>4_000</result>