The perimeter of a rectangular vegetable field is 100 meters, and the length is four times the width. What is the area of the rectangular vegetable field in square meters?
一块长方形菜地的周长是100米，长是宽的4倍，这块长方形菜地的面积是多少平方米．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">100 / 2 / 5</gadget>
<output>10</output>

<gadget id="calculator">4 * 10 * 10</gadget>
<output>400</output>

<result>400</result>