On a map with a scale of (1/3000000), the distance from Beijing to Nanjing is 30.6 centimeters. How many hours does it take for a car to travel from Nanjing to Beijing at a speed of 45 kilometers per hour?
在一幅比例尺是(1/3000000)的地图上，量得北京到南京的距离是30.6厘米．一辆汽车以每小时45千米的速度从南京到北京，约需多少小时才能到达？
<gadget id="calculator">1 / 3_000_000</gadget>
<output>1/3_000_000 = around 0</output>

<gadget id="calculator">30.6 / (1/3_000_000) / 100_000 / 45</gadget>
<output>20.4</output>

<result>20.4</result>