A cone-shaped wood with a base diameter of 6 decimeters is cut vertically along the base diameter, and the surface area is increased by 30 square decimeters. What is the height of the cone in decimeters?
把一个底面直径6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，圆锥体的高是多少分米．
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">2 / 6</gadget>
<output>1/3 = around 0.333333</output>

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

<result>5</result>