There are 5 football teams playing a football match. If every 2 teams play 1 match, how many games are there in total?
有5支足球队进行足球比赛，如果每两支球队进行一场比赛，共比多少场．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">4 * (5/2)</gadget>
<output>10</output>

<result>10</result>