A truck travels from A to B at a speed of 60 km/h, and another truck travels from B to A at a speed of 75 km/h. After 4 hours two trucks meet, how many kilometers are the distance between A and B?
一辆货车从甲地开往乙地，速度是60千米/小时，另一辆货车从乙地开往甲地，速度是75千米/小时．经过4小时两辆货车相遇，甲、乙两地相距多少千米．
<gadget id="calculator">60 + 75</gadget>
<output>135</output>

<gadget id="calculator">135 * 4</gadget>
<output>540</output>

<result>540</result>