Two people, A and B, run along a 400-meter circular track. They start from the same place at the same time and walk in the same direction. A's speed is 280 m/min and B's speed is 240 m/min. How many minutes did it take for A to catch up with B for the first time?
甲、乙两人沿着400米的环形跑道跑步，他们同时从一地点出发，同向而行．甲的速度是280米/分，乙的速度是240米/分．经过多少分钟甲第一次追上乙？
<gadget id="calculator">280 - 240</gadget>
<output>40</output>

<gadget id="calculator">400 / 40</gadget>
<output>10</output>

<result>10</result>