Two trains, A and B, are running towards each other at the same time from two places 700 kilometers apart. Train A travels 85 kilometers per hour, and train B travels 90 kilometers per hour. How long will the two trains meet?
甲、乙两列火车同时从相距700千米的两地相向而行，甲列车每小时行85千米，乙列车每小时行90千米，几小时两列火车相遇？
<gadget id="calculator">85 + 90</gadget>
<output>175</output>

<gadget id="calculator">700 / 175</gadget>
<output>4</output>

<result>4</result>