The inner diameter of a ring is 2 cm, the outer diameter is 3 cm, what is the area of the ring in cm**2.
一个圆环内直径为2cm，外直径为3cm，圆环的面积为多少cm**2．
<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">(3/2) ** 2</gadget>
<output>9/4 = around 2.25</output>

<gadget id="calculator">3.14 * (9/4)</gadget>
<output>7.065</output>

<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<gadget id="calculator">7.065 - 3.14</gadget>
<output>3.925</output>

<result>3.925</result>