After the length and width of a rectangle are increased by 10 cm, the area of the new rectangle is 500 cm2 larger than the original area, find the perimeter of the original rectangle.
一个长方形长和宽都增加10厘米后，得到新的长方形面积比原来增加500平方厘米，求原来长方形的周长．
<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<result>80</result>