Cut a circle with a diameter of 10 decimeters into two semicircles along a diameter, what is the sum of the perimeters of the two semicircles?
把一个直径是10分米的圆形沿一条直径剪成两个半圆，这两个半圆形的周长的和是多少分米．
<gadget id="calculator">3.14 * 10</gadget>
<output>31.4</output>

<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">31.4 + 20</gadget>
<output>51.4</output>

<result>51.4</result>