person walks at a speed of 2 meters per second. A train came from behind and passed him by 10 seconds. It is known that the train is 90 meters long. Find the speed of the train.
某人步行的速度为每秒2米．一列火车从后面开来，超过他用了10秒．已知火车长90米．求火车的速度．
<gadget id="calculator">90 / 10</gadget>
<output>9</output>

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

<result>11</result>