If the perimeter of a semicircle with a radius of 2dm is equal to the perimeter of a rectangle, and the ratio of the length to width of the rectangle is 3:1, what is the area of the rectangle?
一个半径是2dm的半圆的周长和一个长方形的周长相等，而且长方形的长和宽的比是3：1，则这个长方形面积是多少．
<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

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

<gadget id="calculator">6.28 + 4</gadget>
<output>10.28</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">10.28 * (3/4)</gadget>
<output>7.71</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">10.28 * (1/4)</gadget>
<output>2.57</output>

<gadget id="calculator">7.71 * 2.57</gadget>
<output>19.8147</output>

<result>19.8147</result>