In ancient my country, various patterns were often carved on various jade stones. A circular jade pendant from the Tang Dynasty unearthed in Shaanxi has an outer radius of 4 cm and an inner radius of 3 cm. What is the area of this jade pendant in square centimeters?
我国古代常在各种玉石上雕琢各种花纹．陕西出土的一块唐朝环形玉佩，它的外圆半径是4厘米，内圆半径是3厘米，这块玉佩的面积是多少平方厘米？
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">16 - 9</gadget>
<output>7</output>

<gadget id="calculator">3.14 * 7</gadget>
<output>21.98</output>

<result>21.98</result>