If the perimeter of a square is 60 centimeters, what is its area in square centimetres?
一个正方形的周长是60厘米，它的面积是多少平方厘米．
<gadget id="calculator">60 / 4</gadget>
<output>15</output>

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

<result>225</result>