A rectangle is 40 meters long and its length is twice its width. What is the perimeter of this rectangle?
一个长方形长40米，长是宽的2倍，这个长方形的周长是多少米？
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">40 + 20</gadget>
<output>60</output>

<gadget id="calculator">60 * 2</gadget>
<output>120</output>

<result>120</result>