A sheep is tied to a tree stump in the middle of a grass field. The length of the rope from the tree stump to the neck of the sheep is 2.5 meters. How many square meters of grass can the sheep eat?
一只羊栓在一块草地中央的树桩上，树桩到羊颈的绳长是2.5米，这只羊可以吃到多少平方米地面的草？
<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>