train of passenger cars and a train of trucks are traveling towards each other from two places 405 kilometers apart. After 4.5 hours, the two cars meet. It is known that the passenger car travels 50 kilometers per hour. How many kilometers per hour does the truck travel?
一列客车与一列货车从相距405千米的两地相向而行，经过4.5小时两车相遇，已知客车每小时行驶50千米，货车每小时行驶多少千米？
<gadget id="calculator">405 / 4.5</gadget>
<output>90</output>

<gadget id="calculator">90 - 50</gadget>
<output>40</output>

<result>40</result>