If the radius of the base of the cylinder is doubled, and the height is doubled, its lateral area will be doubled.
把圆柱的底面半径扩大到原来的2倍，高也扩大到原来的2倍，它的侧面积就扩大到原来的多少倍．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<result>4</result>