To build a road, the ratio of what has already been built to the total length is 1:3. If another 150 meters are built, half of the road can be completed. How many meters is the total length of this road?
修一条路，已经修的和全长的比是1：3，如果再修150米，就可完成这条路的一半，这条路全长多少米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/2) - (1/3)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">150 / (1/6)</gadget>
<output>900</output>

<result>900</result>