If the perimeter of a square is 60 decimeters, what is its area in square decimeters?
正方形的周长是60分米，它的面积是多少平方分米．
<gadget id="calculator">60 / 4</gadget>
<output>15</output>

<gadget id="calculator">15 * 15</gadget>
<output>225</output>

<result>225</result>