On a map, the distance on the map between A and B is 4 cm, and the distance on the map between B and C is 10 cm. If the actual distance between B and C is 40 kilometers, then how many kilometers is the actual distance between A and B?
在一幅地图上，甲乙两地之间的图上距离是4厘米，乙丙两地之间的图上距离是10厘米．如果乙丙两地之间的实际距离是40千米，那么甲乙两地之间的实际距离是多少千米？
<gadget id="calculator">40 * 100_000</gadget>
<output>4_000_000</output>

<gadget id="calculator">10 / 4_000_000</gadget>
<output>1/400_000 = around 0.000002</output>

<gadget id="calculator">4 / (1/400_000) / 100_000</gadget>
<output>16</output>

<result>16</result>