Two vehicles, A and B, set off from A and B at the same time, drive toward each other, and drive back and forth between A and B continuously. After A arrives at B, it stays at B for 3 hours, and then returns to A; B After the car arrives at point A, it immediately returns to point B; the two cars meet again on the way back, and the place where they meet is 315 kilometers away from point B. It is known that the speed of car A is 90 kilometers per hour, and the speed of car B is 70 kilometers per hour. Question: How far is the distance between A and B?
甲、乙两车同时从A、B两地出发，相向而行，在A、B之间不断往返行驶，甲车到达B地后，在B地停留了3个小时，然后返回A地；乙车到达A地后，马上返回B地；两车在返回的途中又相遇了，相遇的地点距离B地315千米，已知甲车的速度是每小时90千米，乙车的速度是每小时70千米．请问：A、B两地相距多少千米？
<gadget id="calculator">315 / 70</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">315 / 90</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">(9/2) + (7/2) + 3</gadget>
<output>11</output>

<gadget id="calculator">2 / 70</gadget>
<output>1/35 = around 0.028571</output>

<gadget id="calculator">1 / 90</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">(1/35) - (1/90)</gadget>
<output>11/630 = around 0.01746</output>

<gadget id="calculator">11 / (11/630)</gadget>
<output>630</output>

<result>630</result>