A mountain road is going to be built in a certain place. The first phase of the project has completed 45% of the total length, and the second phase of the project has completed 20% of the total length, leaving 1120 meters to be completed. How long is this road around the mountain?
某地要修一条环山公路，第一期工程修了全长的45%，第二期工程修了全长的20%，还剩下1120米没有修完．这条环山公路长多少米？
<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (9/20) - (1/5)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">1_120 / (7/20)</gadget>
<output>3_200</output>

<result>3_200</result>