If the perimeter of a square is 20 decimeters, what is its side length in centimeters?
一个正方形的周长是20分米，它的边长是多少厘米．
<gadget id="calculator">20 * 10</gadget>
<output>200</output>

<gadget id="calculator">200 / 4</gadget>
<output>50</output>

<result>50</result>