At the senior sports meeting, Uncle Liu participated in the long-distance running competition. The whole course was 2.5km, and it took 15 minutes to finish, and won the first place. Uncle Li also participated in the competition, and he took 2 minutes more than Uncle Liu. How many minutes does Uncle Li take on average to run 1km?
在老年运动会上，刘大伯参加了长跑比赛．全程2.5km，用了15分钟跑完，获得了第一名．李大伯也参加了比赛，他比刘大伯多用了2分钟．李大伯跑1km平均需要多少分钟．
<gadget id="calculator">15 + 2</gadget>
<output>17</output>

<gadget id="calculator">17 / 2.5</gadget>
<output>6.8</output>

<result>6.8</result>