If two rectangles 4 cm long and 2 cm wide are put together to form a square, what is the area in square centimetres?
用两个长4厘米、宽2厘米的长方形拼成一个正方形后，面积是多少平方厘米．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<result>16</result>