The radius of the base of a cylinder is 5dm, if the height increases by 2dm, how much does the side area increase by dm**2.
一个圆柱的底面半径是5dm，若高增加2dm，则侧面积增加多少dm**2．
<gadget id="calculator">2 * 3.14 * 5 * 2</gadget>
<output>62.8</output>

<result>62.8</result>