The distance between A and B is 50 kilometers, and it is 10 centimeters drawn on a plan; if the distance between B and C is 20 kilometers, how many centimeters should be drawn on the same plan.
A、B两地的距离是50千米，画在一幅平面图上是10厘米；如果B、C两地的距离是20千米，画在同一幅平面图上，应画多少厘米．
<gadget id="calculator">50 * 100_000</gadget>
<output>5_000_000</output>

<gadget id="calculator">10 / 5_000_000</gadget>
<output>1/500_000 = around 0.000002</output>

<gadget id="calculator">20 * 100_000 * (1/500_000)</gadget>
<output>4</output>

<result>4</result>