If a sheep is tied to a tree with a rope 5 meters long, how much grass can it eat?
一只羊用一根长5米的绳子拴在树上，它可以吃到多大面积的草？
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<result>78.5</result>