18 students have a badminton match. If every two players play one game, how many games will it take in total?
18名同学进行羽毛球比赛，如果每两个人赛一场，一共要多少场．
<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<gadget id="calculator">17 / 2</gadget>
<output>17/2 = around 8.5</output>

<gadget id="calculator">18 * (17/2)</gadget>
<output>153</output>

<result>153</result>