A and B start from places A and B, which are 120 kilometers apart. A’s speed is 20 kilometers per hour, and B’s speed is 10 kilometers per hour. How long will it take to meet each other?
甲乙分别从相距120千米的A、B两地出发，甲的速度是每小时20千米，乙的速度是每小时10千米，那么经过多久可以相遇？
<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">120 / 30</gadget>
<output>4</output>

<result>4</result>