In a party attended by 13 persons, each clinch their glass with every other. How many glass clinches?	Choose the correct option.
A) 51  B) 52  C) 78  D) 54  E) 55
Total no. of person = 11   Total no. of glass clinches = n(n-1)/2   =13*12/2= 
<gadget id="calculator">13*12/2</gadget>
<output>78</output>
78   ANSWER:78
<result>C</result>
In a party attended by 13 persons, each clinch their glass with every other. How many glass clinches?