To build a road, the ratio of the repaired length to the unrepaired length is 1:3. After repairing 300 meters, the ratio of the repaired length to the unrepaired length is 1:2. How many meters is this road?
修一条公路，已修和未修长度的比是1：3，再修300米后，已修和未修长度的比是1：2，这条公路有多少米．
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

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

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(3/4) - (2/3)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">300 / (1/12)</gadget>
<output>3_600</output>

<result>3_600</result>