If a square with a side length of 3 cm is enlarged by 3:1, what is the area in square centimeters?
把一个边长是3厘米的正方形按3：1放大后，面积是多少平方厘米．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">9 * 9</gadget>
<output>81</output>

<result>81</result>