Xiao Ming and Xiao Hua run along a 400-meter circular track. They start from the same place at the same time and walk in the same direction. Xiao Ming runs 280 meters per minute, and Xiao Hua runs 240 meters per minute. How many minutes did it take for Xiao Ming to catch up with Xiao Hua for the first time?
小明和小华两人沿着400米的环形跑道跑步，他们两人同时从同一个地点出发，同向而行，小明每分钟跑280米，小华每分钟跑240米．经过多少分钟小明第一次追上小华？
<gadget id="calculator">280 - 240</gadget>
<output>40</output>

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

<result>10</result>