If a cone-shaped wood with a base circumference of 31.4 decimeters is cut vertically along the diameter of the base, the surface area is increased by 30 square decimeters, what is the volume of the cone in cubic decimeters?
把一个底面周长31.4分米的圆锥形木料沿底面直径竖直剖开，表面积增加30平方分米，圆锥体的体积多少立方分米．
<gadget id="calculator">31.4 / 3.14</gadget>
<output>10</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15 * (1/5)</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">3.14 * 25 * 3 * (1/3)</gadget>
<output>78.5</output>

<result>78.5</result>