A piece of rectangular paper with a length of 20 cm and a width of 15 cm forms a cylinder, what is the lateral area of the cylinder?
一张长方形纸，长20厘米，宽15厘米，把它围成一个圆柱，圆柱的侧面积是多少．
<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<result>300</result>