Qianjin Iron and Steel Works uses two cars to transport ore from a mine 90 kilometers away from the factory. There are two cars, A and B. Car A comes from the mine, and car B starts from the iron and steel plant at the same time and travels towards each other at a speed of 40 kilometers per hour. If the loading and unloading time is not counted, and the two vehicles do not make any stops, how many kilometers away will the two vehicles be from the mine when they meet for the third time?
前进钢铁厂用两辆汽车从距工厂90千米的矿山运矿石，现有甲、乙两辆汽车，甲车自矿山，乙车自钢铁厂同时出发相向而行，速度分别为每小时40千米和50千米，到达目的地后立即返回，如此反复运行多次，如果不计装卸时间，且两车不作任何停留，则两车在第三次相遇时，距矿山多少千米？
<gadget id="calculator">90 * 2</gadget>
<output>180</output>

<gadget id="calculator">90 + 180 + 180</gadget>
<output>450</output>

<gadget id="calculator">40 + 50</gadget>
<output>90</output>

<gadget id="calculator">450 / 90</gadget>
<output>5</output>

<gadget id="calculator">40 * 5</gadget>
<output>200</output>

<gadget id="calculator">2 * 90</gadget>
<output>180</output>

<gadget id="calculator">200 - 180</gadget>
<output>20</output>

<result>20</result>