A 180-meter-long passenger car is traveling west at a speed of 78 km/h, and another 460-meter-long truck is traveling eastward. They meet at the east end of a 210-meter-long railway bridge and separate at the west end. What is the speed of the truck in km/h.
一列长180米的客车以78千米/小时的速度向西行驶，另一列长460米的货车向东行驶，它们在一座长210米铁路桥东端相遇，西端相离．货车的速度是多少千米/小时．
<gadget id="calculator">460 - 210</gadget>
<output>250</output>

<gadget id="calculator">250 / 1_000</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">180 + 210</gadget>
<output>390</output>

<gadget id="calculator">390 / 1_000 / 78</gadget>
<output>1/200 = around 0.005</output>

<gadget id="calculator">(1/4) / (1/200)</gadget>
<output>50</output>

<result>50</result>