The perimeter of a rectangle is 40 cm, and the ratio of length to width is 3:2. Draw the largest circle in this rectangle. What is the area of this circle?
一个长方形的周长是40厘米，长与宽的比是3：2，在这个长方形里画一个最大的圆，这个圆的面积是多少．
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 * (2/5)</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<result>50.24</result>