The perimeter of a rectangle is 42 cm, and the ratio of length to width is 4:3. What is the area of the rectangle in square centimeters?
一个长方形的周长为42厘米，长和宽的比是4：3，这个长方形的面积是多少平方厘米．
<gadget id="calculator">42 / 2</gadget>
<output>21</output>

<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">21 * (4/7)</gadget>
<output>12</output>

<gadget id="calculator">21 - 12</gadget>
<output>9</output>

<gadget id="calculator">12 * 9</gadget>
<output>108</output>

<result>108</result>