To build a road, the full length (2/5) has been built, and after another 420 meters, the remaining full length (1/4) has not been repaired. How many meters is the total length of this road?
修一条路，已修了全长的(2/5)，再修420米后，剩下全长的(1/4)没有修，这条公路全长多少米？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/4) - (2/5)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">420 / (7/20)</gadget>
<output>1_200</output>

<result>1_200</result>