On a map with a scale of 1:20000000, the distance between the airports of A and B is measured to be 6 cm. How many hours does it take for a passenger plane to fly from the airport of A to the airport of B at a speed of 400 kilometers per hour.
在一幅比例尺是1：20000000的地图上，量得甲乙两地机场相距6厘米，一架客机以每小时400千米的速度从甲地机场飞往乙地机场，需要飞行多少小时多少．
<gadget id="calculator">1 / 20_000_000</gadget>
<output>1/20_000_000 = around 0</output>

<gadget id="calculator">6 / (1/20_000_000) / 100_000 / 400</gadget>
<output>3</output>

<result>3</result>