If 6 persons meet at a reunion and each person shakes hands exactly once with each of the others, what is the total number of handshakes?
Pick:
A) 6 × 5 × 4 × 3 × 2 × 1	B) 6 × 5 × 4 × 3 × 2 × 1	C) 6 x 5	D) 15	E) 45
1st person will have 5 handshakes, 2nd will have 4, ....5th will have 1 and 6th will have 0   = 5+4+3+2+1= 
<gadget id="calculator">5+4+3+2+1</gadget>
<output>15</output>
15   if we generalize this: if there are n people then there will be n(n-1)/2 handshakes.   Ans.15)
<result>D</result>
If 6 persons meet at a reunion and each person shakes hands exactly once with each of the others, what is the total number of handshakes?