Xiaoqing got on a train and found that it took 90 seconds for the train to pass through the 1500-meter tunnel and 40 seconds to cross the 600-meter bridge. What is the length of the train in meters?
小青乘上了一列火车，发现这列火车穿过1500米的隧道花了90秒，越过600米的桥梁花了40秒，则这列火车的长是多少米．
<gadget id="calculator">1_500 - 600</gadget>
<output>900</output>

<gadget id="calculator">90 - 40</gadget>
<output>50</output>

<gadget id="calculator">900 / 50</gadget>
<output>18</output>

<gadget id="calculator">90 * 18</gadget>
<output>1_620</output>

<gadget id="calculator">1_620 - 1_500</gadget>
<output>120</output>

<result>120</result>