What is the perimeter of a semicircle with a diameter of 12 decimeters?
直径为12分米的半圆形的周长为多少分米．
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">3.14 * 6</gadget>
<output>18.84</output>

<gadget id="calculator">18.84 + 12</gadget>
<output>30.84</output>

<result>30.84</result>