The school playground is a rectangle with a length of 130 meters and a width of 40 meters. A green belt is planted around it. The length of the green belt is at least how many meters.
学校操场是一个长130米，宽40米的长方形，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>