The perimeter of a rectangle is 40 meters and the ratio of length to width is 4:1. What is the area of the rectangle in square meters?
长方形的周长是40米，长和宽的比是4：1．长方形的面积是多少平方米？
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">20 * (1/5)</gadget>
<output>4</output>

<gadget id="calculator">(1/5) / 5</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">20 * (1/25)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20 * (4/5) * 20 * (1/5)</gadget>
<output>64</output>

<result>64</result>