On a map with a scale of 1:9000000, the distance between A and B is 5 cm. If two cars drive from A and B at the same time, their speeds are 30 kilometers per hour and 45 kilometers, how many hours will the two cars meet?
在一幅比例尺为1：9000000的地图上量得A、B两地的距离是5厘米，如果有两辆汽车同时从A、B两地相对开出，速度分别为每小时行30千米和45千米，问两辆汽车经过几小时后相遇？
<gadget id="calculator">1 / 9_000_000</gadget>
<output>1/9_000_000 = around 0</output>

<gadget id="calculator">30 + 45</gadget>
<output>75</output>

<gadget id="calculator">5 / (1/9_000_000) / 100_000 / 75</gadget>
<output>6</output>

<result>6</result>