A person is riding a bicycle along a road parallel to the railway. A train is coming from behind. It takes 20 seconds to pass by. The length of the train is 240m and the speed is 16m/s. What is the speed of this person?
某人沿着与铁路平行的公路骑车前进，一列火车从后面开来，在身旁通过的时间是20秒，火车长240m，速度16m/s，这人骑车速度是多少？
<gadget id="calculator">240 / 20</gadget>
<output>12</output>

<gadget id="calculator">16 - 12</gadget>
<output>4</output>

<result>4</result>