A cylinder has a base diameter of 10 cm and a height of 4 decimeters, what is its lateral area?
一个圆柱的底面直径是10厘米，高是4分米，它的侧面积是多少？
<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<gadget id="calculator">3.14 * 10 * 40</gadget>
<output>1_256</output>

<result>1_256</result>