A square playground has a perimeter of 120 meters, what is its area?
一个正方形操场，周长是120米，它的面积有多大？
<gadget id="calculator">120 / 4</gadget>
<output>30</output>

<gadget id="calculator">30 * 30</gadget>
<output>900</output>

<result>900</result>