It took a train 30 seconds to pass through a 430-meter-long bridge. When it passed through a 2180-meter-long tunnel, its speed was doubled, and it took only 50 seconds. How long is the train?
一列火车通过一座长430米的大桥用了30秒，它通过一条长2180米的隧道时，速度提高了一倍，结果只用了50秒，这列火车长多少米．
<gadget id="calculator">2_180 - 430</gadget>
<output>1_750</output>

<gadget id="calculator">100 - 30</gadget>
<output>70</output>

<gadget id="calculator">1_750 / 70</gadget>
<output>25</output>

<gadget id="calculator">30 * 25</gadget>
<output>750</output>

<gadget id="calculator">750 - 430</gadget>
<output>320</output>

<result>320</result>