The perimeter of a semicircular flowerbed is 51.4 meters, 50% of this flowerbed is planted with rose flowers, what is the area of rose flowers?
一个半圆形花圃的周长是51.4米，这个花圃的50%种月季花，月季花的面积是多少．
<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">100 / 2</gadget>
<output>50</output>

<gadget id="calculator">3.14 * 50</gadget>
<output>157</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">157 * (1/2)</gadget>
<output>157/2 = around 78.5</output>

<result>157/2 = around 78.5</result>