Two cars, fast and slow, drive towards each other from places A and B. The fast car travels 60 km per hour, the slow car travels 40 km per hour, and the slow car starts an hour earlier. In this way, the two cars meet at the midpoint. How many kilometers are the distance between A and B?
快慢两车从甲乙两地相向而行，快车每小时行60km，慢车每小时行40km，慢车先出发一小时，这样两车刚好在中点相遇，甲乙两地相距多少千米？
<gadget id="calculator">40 * 3</gadget>
<output>120</output>

<gadget id="calculator">120 + 120</gadget>
<output>240</output>

<result>240</result>