football teams have a friendly match, each of the two teams will play one game, how many games will there be in total?
5个足球队举行友谊比赛，每两个队都要赛一场，一共要比赛多少场．
<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>