After combining two squares of the same size into a rectangle, the perimeter is 10 decimeters less than the sum of the perimeters of the original two squares. What is the perimeter of the original square in decimeters?
用两个大小完全相同的正方形拼成一个长方形后，周长比原来两个正方形的周长总和少了10分米，原来一个正方形的周长是多少分米．
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>