There will be a tug-of-war competition between the 4 classes of the sixth grade, and the competition will be played in a single round-robin system. How many games will be played in the whole grade?
六年级4个班之间将举行拔河比赛，采用单循环制进行比赛，全年级一共要进行多少场比赛．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<result>6</result>