If the radius of a semicircle is 5 cm, what is the circumference of the semicircle in cm?
如果一个半圆的半径是5厘米，那么这个半圆的周长是多少厘米．
<gadget id="calculator">3.14 * 5</gadget>
<output>15.7</output>

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

<gadget id="calculator">15.7 + 10</gadget>
<output>25.7</output>

<result>25.7</result>