The perimeter of a rectangular classroom floor is 42 meters, and the ratio of length to width is 4:3. How many square meters is the floor area of this rectangular classroom?
一间长方形教室地面的周长是42米，长与宽的比是4：3，这间长方形教室地面的面积是多少平方米？
<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>