The distance between A and B is 309km. A passenger car drives from A to B. After 1.5 hours, a truck drives from B to A. The truck travels 40km per hour, and the bus travels 42km per hour. After several hours of driving Can two cars meet?
甲、乙两地相距309km，一辆客车从甲地开往乙地，1.5h后一辆货车从乙地开往甲地，货车每小时行40km，客车每小时行42km，货车行驶几小时后两车才能相遇？
<gadget id="calculator">42 * 1.5</gadget>
<output>63</output>

<gadget id="calculator">309 - 63</gadget>
<output>246</output>

<gadget id="calculator">42 + 40</gadget>
<output>82</output>

<gadget id="calculator">246 / 82</gadget>
<output>3</output>

<result>3</result>