A train of passenger cars and a train of freight trains depart from two cities A and B at the same time. The passenger train travels 120 km per hour, and the freight train travels 90 km per hour. After 3.5 hours, the two trains meet. How long is the railway line between A and B?
一列客车和一列货车同时从甲、乙两个城市相对开出，客车每小时行120km，货车每小时行90km，经过3.5小时两车相遇．甲、乙两个城市间的铁路线长多少千米？
<gadget id="calculator">120 + 90</gadget>
<output>210</output>

<gadget id="calculator">210 * 3.5</gadget>
<output>735</output>

<result>735</result>