Zhangjia Village is going to build a country road. The first phase of the project has repaired 50% of the total length, and the second phase of the project has repaired 30% of the total length. There are still 800 meters left to be repaired. How long is the total length of this road?
张家村要修一条乡间小路，第一期工程修了全长的50%，第二期工程修了全长的30%，还剩下800米没有修，这条小路全长多少米？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">800 / (1/5)</gadget>
<output>4_000</output>

<result>4_000</result>