To build a road, the ratio of the length of the repaired part to the length of the unrepaired part is 1:5. After another 490 meters are repaired, the length of the repaired part is three times that of the unrepaired part. How long is this road in meters?
修一条路，已修好的与未修好的长度比是1：5，再修490米后，已修好的是未修的3倍．这条路全长多少米？
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 + 5</gadget>
<output>6</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(3/4) - (1/6)</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">490 / (7/12)</gadget>
<output>840</output>

<result>840</result>