Two cargo ships A and B sail from port A to port B at the same time. Ship A travels 20 kilometers more per hour than ship B. Ship A arrives at point C on the way 3 hours earlier than ship B. When ship B arrives at point C, A The boat just arrives at B, find the distance between A and B.
A、B两艘货轮同时从甲港口开往乙港口，A船比B船每小时多行20千米，A船比B船早3小时到达中途丙处，当B船到达丙处时，A船刚好到达乙处，求甲、乙间的距离．
<gadget id="calculator">20 + 20</gadget>
<output>40</output>

<gadget id="calculator">40 * 3 * 2</gadget>
<output>240</output>

<result>240</result>