The actual distance between A and B is 900km, and the actual distance between A and C is 780km. Draw them on the same map, if the straight-line distance on the map between A and B is 15cm, then what is the straight-line distance on the map between A and C?
甲、乙两地的实际距离是900km，甲、丙两地的实际距离是780km．把它们画在同一幅地图上，如果甲、乙两地的图上直线距离是15cm，那么甲、丙两地的图上直线距离是多少？
<gadget id="calculator">900 * 100_000</gadget>
<output>90_000_000</output>

<gadget id="calculator">15 / 90_000_000</gadget>
<output>1/6_000_000 = around 0</output>

<gadget id="calculator">780 * 100_000 * (1/6_000_000)</gadget>
<output>13</output>

<result>13</result>