A passenger car drives from place A to place B, which is 550 kilometers away, and travels 40 kilometers per hour. One hour after driving, a truck travels from place B to place A, traveling 45 kilometers per hour. How many hours did the truck meet the passenger car?
一辆客车从甲地驶往相距550千米的乙地，每小时行40千米，开出1小时后，一辆货车从乙地开往甲地，每小时行45千米．货车开出几小时后与客车相遇？
<gadget id="calculator">550 - 40</gadget>
<output>510</output>

<gadget id="calculator">40 + 45</gadget>
<output>85</output>

<gadget id="calculator">510 / 85</gadget>
<output>6</output>

<result>6</result>