A walks 80 meters per minute, and B rides a bicycle at 200 meters per minute. The two walk towards each other at the same time for 3 minutes.
甲步行每分钟行80米，乙骑自行车每分钟200米，二人同时同地相背而行3分钟后，乙立即调头来追甲，再经过多少分钟乙可追上甲．
<gadget id="calculator">80 + 200</gadget>
<output>280</output>

<gadget id="calculator">200 - 80</gadget>
<output>120</output>

<gadget id="calculator">3 / 120</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">280 * (1/40)</gadget>
<output>7</output>

<result>7</result>