A passenger ship sails from port A to port B, and a cargo ship sails from port B to port A. The two ships sail towards each other at the same time and meet each other for 6 hours. Continue driving for 2 hours after meeting. At this time, the passenger ship is still 100 kilometers away from port B, and the cargo ship is still 180 kilometers away from port A. How many kilometers is the distance between port A and port B?
客船从甲港开往乙港，货船从乙港开住甲港，两船同时相向开出6小时相遇．相遇后继续行驶2小时，这时客船离乙港还有100千米，货船离甲港还有180千米，甲、乙两港相距多少千米？
<gadget id="calculator">100 + 180</gadget>
<output>280</output>

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

<gadget id="calculator">(1/6) * 2</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">280 / (2/3)</gadget>
<output>420</output>

<result>420</result>