There are 5 children participating in a table tennis match, and every two players will play a game, how many games will be played in total.
有5个小朋友参加乒乓球比赛，每两个人进行一场比赛，一共要打多少场比赛．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">4 * (1/2)</gadget>
<output>2</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<result>10</result>