There is a circular pool with a radius of 5 meters. How many meters does it take to walk around the pool?
有一个圆形水池的半径是5米，绕水池走一圈，要走多少米．
<gadget id="calculator">3.14 * 2 * 5</gadget>
<output>31.4</output>

<result>31.4</result>