For a square with a side length of 3 cm, if the side length is doubled, the area will be doubled by how many times.
边长3厘米的正方形，边长扩大2倍，面积扩大多少倍．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 * 6</gadget>
<output>36</output>

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">36 / 9</gadget>
<output>4</output>

<result>4</result>