There are 6 teams participating in the game, and a game will be held between every two balls. How many games will be held in total.
有6支球队参加比赛，每两支球之间都要举行一场比赛，一共要举行多少场比赛．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

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

<gadget id="calculator">6 * (5/2)</gadget>
<output>15</output>

<result>15</result>