circular vegetable field has a diameter of 20 meters, and (1/4) of the area is reserved for planting eggplants. How many square meters does the eggplant occupy?
一块圆形蔬菜地，它的直径是20米，在它里面留(1/4)的面积种茄子，茄子的占地面积是多少平方米？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

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

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

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">314 * (1/4)</gadget>
<output>157/2 = around 78.5</output>

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