If one side of a square is reduced by 40% and the other side is increased by 6 meters, the resulting rectangle is exactly equal to the area of the original square, what is the area of the square?
一个正方形，如果一边减少40%，另一边增加6米，所得到的长方形与原来正方形面积正好相等，那么正方形面积是多少．
<gadget id="calculator">3.6 / 0.4</gadget>
<output>9</output>

<gadget id="calculator">9 * 9</gadget>
<output>81</output>

<result>81</result>