On a map with a scale of 1:5000000, the distance from A to B is 9 cm. Two cars, A and B, drive from two places at the same time and meet each other after 5 hours. Car A travels 50 kilometers per hour. How many kilometers does car B travel per hour?
在一幅比例尺是1：5000000的图上，量得A地到B地的距离是9厘米．甲乙两辆汽车同时从两地相对开出，5小时后相遇，甲车每小时行50千米，乙车每小时行多少千米？
<gadget id="calculator">1 / 5_000_000</gadget>
<output>1/5_000_000 = around 0</output>

<gadget id="calculator">9 / (1/5_000_000) / 100_000 / 5</gadget>
<output>90</output>

<gadget id="calculator">90 - 50</gadget>
<output>40</output>

<result>40</result>