There is a bamboo fence around a semicircular vegetable field. The radius of the semicircular vegetable field is 5 meters. How long is the bamboo fence?
一个半圆形菜地的周围要围一圈竹篱笆，半圆形菜地的半径为5米，这个竹篱笆长多少米．
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">3.14 * 2 * (5/2)</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>