It takes 7 hours for the express train to travel from station A to station B, and it takes 2 hours longer for the local train to travel from station A to station B than the express train. It is known that the express train travels 16 kilometers more per hour than the slow train, how many kilometers are the distance between A and B?
快车从A站开往B站需要7小时，慢车从A站开往B站的时间比快车多用2小时．已知快车每小时比慢车多行16千米，A、B两站相距多少千米？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/7) - (1/9)</gadget>
<output>2/63 = around 0.031746</output>

<gadget id="calculator">16 / (2/63)</gadget>
<output>504</output>

<result>504</result>