If a circle with a radius of 2.5 decimeters is cut into a semicircle, what is the circumference of the semicircle?
把一个半径是2.5分米的圆剪成一个半圆，半圆的周长是多少分米．
<gadget id="calculator">3.14 * 2.5</gadget>
<output>7.85</output>

<gadget id="calculator">2.5 * 2</gadget>
<output>5</output>

<gadget id="calculator">7.85 + 5</gadget>
<output>12.85</output>

<result>12.85</result>