The speeds of three cars A, B, and C are 50 km/h, 60 km/h, and 70 km/h respectively. Car A and B start from point A, and car C starts from point B at the same time. When C encounters B, 15 minutes later Meet A again, find the distance between A and B.
甲乙丙三辆汽车的速度分别为50千米/小时、60千米/小时、70千米/小时，甲乙两车从A地，丙车从B地同时相对出发，丙遇到乙15分钟后又遇到甲，求A，B两地的距离．
<gadget id="calculator">50 + 70</gadget>
<output>120</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">60 - 50</gadget>
<output>10</output>

<gadget id="calculator">(1/4) / 10</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">60 + 70</gadget>
<output>130</output>

<gadget id="calculator">120 * (1/40) * 130</gadget>
<output>390</output>

<result>390</result>