Eleven sixth graders in a certain school participate in a table tennis match. If every two students shake hands once, how many times should they shake hands in total?
某校六年级11位同学参加乒乓球比赛，如果每两人握一次手，一共要握多少次手．
<gadget id="calculator">11 - 1</gadget>
<output>10</output>

<gadget id="calculator">11 / 2</gadget>
<output>11/2 = around 5.5</output>

<gadget id="calculator">10 * (11/2)</gadget>
<output>55</output>

<result>55</result>