Cut a largest square out of a rectangle with a length of 8 decimeters and an area of 40 square decimeters. What is the area of this square?
在一个长8分米，面积是40平方分米的长方形里剪出一个最大的正方形，这个正方形的面积是多少．
<gadget id="calculator">40 / 8</gadget>
<output>5</output>

<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<result>25</result>