The express train runs from A to B, and the slow train travels from B to A. The two trains leave opposite each other at the same time and meet each other in 9 hours. After meeting, the two cars continue to drive at the original speed, and the express train arrives at point B after another 6 hours, and the slow train is still 420 kilometers away from point A. How many kilometers are there between A and B?
快车从甲地开往乙地，慢车从乙地开往甲地，两车同时相对开出，9小时相遇．相遇后，两车按原速继续行驶，又经6小时快车到达乙地，慢车离甲地还有420千米．甲乙两地相距多少千米？
<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/9) * 6</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">420 / (1/3)</gadget>
<output>1_260</output>

<result>1_260</result>