If the perimeter of a rectangle is 100 cm and the width is 1/4 of the length, what is the area of the rectangle in square centimeters?
一个长方形的周长是100厘米，宽是长的(1/4)，这个长方形的面积是多少平方厘米．
<gadget id="calculator">100 / 2</gadget>
<output>50</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">50 * (4/5)</gadget>
<output>40</output>

<gadget id="calculator">50 - 40</gadget>
<output>10</output>

<gadget id="calculator">40 * 10</gadget>
<output>400</output>

<result>400</result>