The road repair team built a road. On the first day, 40% of the total length was repaired, and on the second day, 20m was repaired. At this time, half of the total length was repaired. How many meters is the total length of this road?
修路队修一条公路，第一天修了全长的40%，第二天修了20m，这时正好修了全长的一半，这条公路全长多少米？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">20 / (1/10)</gadget>
<output>200</output>

<result>200</result>