A rectangular vegetable field is 105 meters long and 45 meters wide. Need to surround this vegetable field with a fence, how long is the fence?
一块长方形菜地，长105米，宽45米．需要给这块菜地围上一圈围栏，围栏有多长？
<gadget id="calculator">105 + 45</gadget>
<output>150</output>

<gadget id="calculator">150 * 2</gadget>
<output>300</output>

<result>300</result>