A circle with a diameter of 5 decimeters is surrounded by a piece of wire. What is the length of the piece of wire?
用一段铁丝围了一个直径是5分米的圆，这段铁丝长多少米．
<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3.14 * (1/2)</gadget>
<output>1.57</output>

<result>1.57</result>