To build a road, 30% of the total length was repaired on the first day, 50% of the total length was repaired on the second day, and 200 meters more were repaired on the second day than on the first day. How long is this road?
修一段公路，第一天修了全长的30%，第二天修了全长的50%，第二天比第一天多修200米，这段公路有多长？
<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">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">200 / (1/5)</gadget>
<output>1_000</output>

<result>1_000</result>