In the summer vacation, Xiaoya, father, mother, grandpa and grandma held a "24 o'clock" family competition. If there is a match between every 2 of the 5 people, how many games will be played in total?
暑假中小亚、爸爸、妈妈、爷爷和奶奶举行"24点"家庭比赛．如果5人中每2人之间都要赛一场，那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>