What is the area of a circle made of a 16m long iron wire with a length of 0.3m at the joint?
用一根长16米的铁丝做成一个圆，接头处长0.3米，这个圆的面积是多少．
<gadget id="calculator">16 - 0.3</gadget>
<output>15.7</output>

<gadget id="calculator">15.7 / 3.14 / 2</gadget>
<output>2.5</output>

<gadget id="calculator">2.5 ** 2</gadget>
<output>6.25</output>

<gadget id="calculator">3.14 * 6.25</gadget>
<output>19.625</output>

<result>19.625</result>