Two trains depart from two places 680 kilometers apart at the same time, the express train travels 108 kilometers per hour, and the slow train travels 62 kilometers per hour. After how many hours do the two trains meet?
两列火车从相距680千米的两地同时相对开出，快车每小时108千米，慢车每小时行62千米，经过几小时两车相遇？
<gadget id="calculator">108 + 62</gadget>
<output>170</output>

<gadget id="calculator">680 / 170</gadget>
<output>4</output>

<result>4</result>