6 children, every two people make a phone call, how many times can they make a phone call?
6个小朋友，每两个人通一次电话，可以通多少次电话．
<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>