Two convoys, A and B, start from two places 840 kilometers apart at the same time and travel toward each other. Convoy A travels 120 kilometers per hour, and convoy B travels 160 kilometers per hour. A person rides a motorcycle and travels 180 kilometers per hour. Contact back and forth between the two convoys, and ask how many kilometers did the motorcycle travel when the two convoys met?
甲、乙两个车队同时从相隔840千米的两地出发相向而行，甲车队每小时行120千米，乙车队每小时行160千米，一个人骑摩托车每小时行180千米，在两车队中间往返联络，问两车队相遇时，摩托车行驶了多少千米？
<gadget id="calculator">120 + 160</gadget>
<output>280</output>

<gadget id="calculator">840 / 280</gadget>
<output>3</output>

<gadget id="calculator">3 * 180</gadget>
<output>540</output>

<result>540</result>