It takes 12 hours for a passenger car to go from city A to city B, and 15 hours for a truck to go from B to A. The two cars drive from the two cities at the same time, and the bus is 180 kilometers away from B when they meet. How many kilometers are the distance between the two cities?
客车从甲城到乙城要12小时，货车从乙到甲需15小时，两车同时从两城相向开出，相遇时客车距乙有180千米，求两城相距多少千米？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/12) + (1/15)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 / (3/20)</gadget>
<output>20/3 = around 6.666667</output>

<gadget id="calculator">(1/15) * (20/3)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">180 / (4/9)</gadget>
<output>405</output>

<result>405</result>