If the diameter of a circular screen is 40 cm, what is its area in square meters?
一个圆形屏幕的直径是40厘米，它的面积是多少平方米．
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">400 / 10_000</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">3.14 * (1/25)</gadget>
<output>0.1256</output>

<result>0.1256</result>