The distance between A and B is 660 kilometers. A car starts from a place and travels 72 kilometers per hour. Another car drives from place B, traveling 48 kilometers per hour. Two cars are driving at the same time, going towards each other, how many hours have passed before they meet?
甲乙两地相距660千米．一辆汽车从甲地开出，每小时行72千米．另一辆汽车从乙地开出，每小时行48千米．两车同时开，相向而行，经过几小时相遇？
<gadget id="calculator">72 + 48</gadget>
<output>120</output>

<gadget id="calculator">660 / 120</gadget>
<output>11/2 = around 5.5</output>

<result>11/2 = around 5.5</result>