6 students in a study group communicate with each other. Every two people have a dialogue. How many times do they have a dialogue in total?
某学习小组6名同学相互交流对话，每两人对话一次，他们一共对话多少次．
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">6 * (5/2)</gadget>
<output>15</output>

<result>15</result>