Two cars depart from the east and west stations at the same time, go towards each other, and meet at a distance of 15 kilometers from the midpoint. It is known that the speed ratio of the two vehicles is 4:7, and how many kilometers are the distance between the east and west stations.
两辆汽车从东、西两站同时出发，相向而行，在离中点15千米处相遇．已知两车的速度比为4：7，东、西两站相距多少千米．
<gadget id="calculator">3 / 11</gadget>
<output>3/11 = around 0.272727</output>

<gadget id="calculator">30 / (3/11)</gadget>
<output>110</output>

<result>110</result>