The perimeter of a rectangle is 20 cm, and the ratio of length to width is 4:1. What is the area of the rectangle?
一个长方形的周长是20cm，长和宽的比是4：1，这个长方形的面积是多少？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

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

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">10 * (4/5)</gadget>
<output>8</output>

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

<gadget id="calculator">10 * (1/5)</gadget>
<output>2</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<result>16</result>