If the length of the rectangle is 8 cm and the width is half the length, what is the circumference in cm?
长方形的长是8厘米，宽是长的一半，周长是多少厘米．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">8 + 4</gadget>
<output>12</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<result>24</result>