Cars A and B drive towards each other at the same time from two places 450 kilometers apart. The speed of car A is 70 kilometers per hour, and the speed of car B is 80 kilometers per hour. How long does it take for the two cars to meet?
甲乙两车同时从相距450千米的两地相向开出．甲车的速度是70千米每小时，乙车的速度时80千米每小时，经过多长时间两车相遇？
<gadget id="calculator">70 + 80</gadget>
<output>150</output>

<gadget id="calculator">450 / 150</gadget>
<output>3</output>

<result>3</result>