The perimeter of a rectangle is 40 cm, which is equal to the perimeter of a square, what is the side length of the square?
一个长方形的周长是40厘米，它与一个正方形的周长相等，正方形的边长是多少．
<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<result>10</result>