If a 20-meter-long iron wire is used to form the largest square, what is the area of the square in square meters?
用一根长20米的铁丝围成一个最大的正方形，这个正方形的面积是多少平方米
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<result>25</result>