Fold a square with a side length of 20 cm in half and cut it along the crease to get two identical rectangles. What is the perimeter of each rectangle in centimeters.
把一张边长是20厘米的正方形对折后，沿着折痕剪开，可以得到两个完全一样的长方形．每个长方形的周长是多少厘米．
<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">2 * 30</gadget>
<output>60</output>

<result>60</result>