A circular piece of paper with a diameter of 20 centimeters, what is the circumference in centimeters after cutting off half of the circle?
一张直径是20厘米的圆形纸片，剪掉半个圆后，它的周长是多少厘米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">3.14 * 10</gadget>
<output>31.4</output>

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

<result>51.4</result>