A circular flower bed has a diameter of 10 meters. Now the flower bed is to be planted with lawn. How many square meters is the area of the lawn?
一个圆形花坛，它的直径是10米，现要将花坛种植草坪，草坪的面积是多少平方米？
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

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

<result>78.5</result>