Draw a rectangle with a perimeter of 16 cm and a ratio of length to width of 3:1. What is the area of the rectangle?
画一个长方形，周长是16厘米，长和宽的比是3：1，这个长方形的面积是多少？
<gadget id="calculator">16 / 2</gadget>
<output>8</output>

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

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

<gadget id="calculator">8 * (3/4)</gadget>
<output>6</output>

<gadget id="calculator">8 - 6</gadget>
<output>2</output>

<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<result>12</result>