For grandpa’s birthday, my mother bought a cylindrical cake with a bottom diameter of 20 decimeters and a height of 12 decimeters. When cutting the cake, it was clearly stated that cutting along the bottom diameter would increase the surface area. Fangfang said that cutting along the bottom surface would increase the surface area. many. Which cut increases the surface area the most? How many square decimeters more?
爷爷过生日，妈妈买来一个底面直径20分米，高12分米的圆柱形蛋糕，切蛋糕时，明明说沿底面直径切开增加的表面积大，芳芳说沿底面切开，增加的表面积多．哪种切法增加的表面积多？多多少平方分米？
<gadget id="calculator">20 * 12 * 2</gadget>
<output>480</output>

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

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<gadget id="calculator">480 - 314</gadget>
<output>166</output>

<result>166</result>