The distance between A and B is 200km. A bus and a truck drive from A to B at the same time. When the bus is 20km away from B, the truck is still 30km away from B. If the two cars are still driving at the original speed, when the passenger car arrives at point B, how many kilometers will the truck be short of reaching point B? (proportional solution)
甲、乙两地相距200km，一辆客车和一辆货车同时从甲地开往乙地，当客车距离乙地20km时，货车距离乙地还有30km．如果两辆车仍然按原速度行驶，当客车到达乙地时，货车还差多少千米到达乙地？(比例解)
<gadget id="calculator">200 - 20</gadget>
<output>180</output>

<gadget id="calculator">200 - 30</gadget>
<output>170</output>

<gadget id="calculator">180 / 170</gadget>
<output>18/17 = around 1.058824</output>

<gadget id="calculator">(18/17) * 30</gadget>
<output>540/17 = around 31.764706</output>

<gadget id="calculator">(540/17) - 20</gadget>
<output>200/17 = around 11.764706</output>

<gadget id="calculator">(200/17) / (18/17)</gadget>
<output>100/9 = around 11.111111</output>

<result>100/9 = around 11.111111</result>