After cutting a cylinder with a height of 6 cm into an approximate cuboid, the surface area increases by 188.4 square centimeters. What is the radius of the cylinder?
把一个高为6厘米的圆柱体切拼成一个近似的长方体后表面积增加了188.4平方厘米，这个圆柱的半径是多少．
<gadget id="calculator">188.4 / 2 / 6</gadget>
<output>15.7</output>

<result>15.7</result>