The school holds grade group football matches. There are 5 teams in the third grade, and there is a match between every 2 teams. How many games will the third grade play in total?
学校举行年级组足球比赛，三年级共有5支球队，每2支球队之间都进行一场比赛．三年级共要进行多少场比赛．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

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

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

<result>10</result>