A water tank has an inner diameter of 54 cm measured from the mouth of the water tank, and a wall thickness of 3 cm. It is necessary to make a head of the water tank so that the head just covers the outer edge of the mouth of the water tank. What is the area of the head in square meters?
一口水缸，从缸口量得它的内直径是54cm，缸壁厚3cm，要制作一个缸盖，使缸盖正好盖住缸口的外沿，这个缸盖的面积是多少平方米？
<gadget id="calculator">54 / 2</gadget>
<output>27</output>

<gadget id="calculator">27 + 3</gadget>
<output>30</output>

<gadget id="calculator">30 ** 2</gadget>
<output>900</output>

<gadget id="calculator">900 / 10_000</gadget>
<output>9/100 = around 0.09</output>

<gadget id="calculator">3.14 * (9/100)</gadget>
<output>0.2826</output>

<result>0.2826</result>