The school playground is an approximate rectangle with a length of 130 meters and a width of 40 meters. A green belt is planted around it. How long is the green belt at least?
学校操场是一个长130米，宽40米的近似的长方形，在它的四周栽上绿化带，绿化带长至少多少米？
<gadget id="calculator">130 + 40</gadget>
<output>170</output>

<gadget id="calculator">170 * 2</gadget>
<output>340</output>

<result>340</result>