On a map with a scale of 1:5,000,000, the distance between cities A and B is 20 cm. If a car starts from city A at a speed of 50 kilometers per hour, how long will it take to reach city B?
在比例尺是1：5000000的地图上，量得A、B两城的距离是20厘米，若一辆汽车以每小时50千米的速度从A城出发，多少小时可以到达B城？
<gadget id="calculator">1 / 5_000_000</gadget>
<output>1/5_000_000 = around 0</output>

<gadget id="calculator">20 / (1/5_000_000) / 100_000 / 50</gadget>
<output>20</output>

<result>20</result>