Two trains are going towards each other, and it takes 15 seconds from the time they meet to miss. The body of A train is 210 meters long and its speed is 18 meters per second. The speed of B train is 12 meters per second. How long is the body of B train?
两列火车相向而行，从碰上到错过用了15秒，甲车车身长210米，车速是每秒18米，乙车车速是每秒12米，乙车车身长多少米？
<gadget id="calculator">18 + 12</gadget>
<output>30</output>

<gadget id="calculator">30 * 15</gadget>
<output>450</output>

<result>450</result>