If a train passes a 200-meter-long bridge at a speed of 60 kilometers per hour and takes 21 seconds, what is the length of the train in meters?
一列火车以每小时60千米的速度通过一座200米长的桥，用了21秒，则火车的车长是多少米．
<gadget id="calculator">1 * 3_600</gadget>
<output>3_600</output>

<gadget id="calculator">1_000 / 3_600</gadget>
<output>5/18 = around 0.277778</output>

<gadget id="calculator">60 * 1 * (5/18) * 21</gadget>
<output>350</output>

<gadget id="calculator">350 - 200</gadget>
<output>150</output>

<result>150</result>