On a map with a scale of 1:4000000, the distance between A and B is 20 cm. Two trains depart from A and B oppositely at the same time. Car A travels 87 kilometers per hour, and train B travels 113 kilometers per hour. How many hours later will the two trains meet?
在比例尺是1：4000000的地图上，量得A、B两地的距离是20厘米．两列火车同时从A、B两地相对开出，甲车每小时行87千米，乙车每小时行113千米，几小时后两车相遇？
<gadget id="calculator">1 / 4_000_000</gadget>
<output>1/4_000_000 = around 0</output>

<gadget id="calculator">87 + 113</gadget>
<output>200</output>

<gadget id="calculator">20 / (1/4_000_000) / 100_000 / 200</gadget>
<output>4</output>

<result>4</result>