8 football teams play a football round robin match (every 2 teams have to play 1 game), how many games will they play in total?
8支足球队进行1场足球循环赛(每2支球队都要踢1场)，一共要踢多少场比赛．
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<result>28</result>