A train is 200 meters long. If the entire train passes through a 400-meter-long tunnel, it will take 10 seconds. At the same speed, it takes 15 seconds for the whole train to pass through a bridge completely. So, what is the length of the bridge in meters?
一列火车长200米，如果整列火车完全通过一条长400米的隧道，需要10秒．若以同样的速度整列火车完全通过一座大桥需要15秒．那么，大桥长是多少米．
<gadget id="calculator">400 + 200</gadget>
<output>600</output>

<gadget id="calculator">600 / 10</gadget>
<output>60</output>

<gadget id="calculator">60 * 15</gadget>
<output>900</output>

<gadget id="calculator">900 - 200</gadget>
<output>700</output>

<result>700</result>