The volume difference between a cylinder and a cone with the same base and height is 6.28 cubic decimeters. What is the sum of the volumes of the cylinder and the cone?
一个圆柱和与它等底等高的圆锥的体积相差6.28立方分米，圆柱和圆锥的体积和是多少立方分米．
<gadget id="calculator">6.28 / 2</gadget>
<output>3.14</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>