A semicircular piece of cardboard is measured to have a circumference of 51.4 cm. What is the area of this piece of paper?
一个半圆硬纸片，量得它的周长是51.4厘米，这个纸片的面积是多少？
<gadget id="calculator">51.4 / 5.14</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<result>314</result>