A person walks at a speed of 2 meters per second. A train came from behind and passed him in 10 seconds. Given that the length of the train is 90 meters, find the speed of the train in meters per second.
某人步行的速度为每秒钟2米．一列火车从后面开来，越过他用了10秒钟．已知火车的长为90米，求列车的速度为多少米/秒．
<gadget id="calculator">90 / 10</gadget>
<output>9</output>

<gadget id="calculator">9 + 2</gadget>
<output>11</output>

<result>11</result>