If 7 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) 7 × 6 × 5 × 4 × 3 × 2 × 1	B) 7 × 6 × 5 × 4 × 3 × 2 × 1	C) 7 x 8	D) 21	E) 45
1st person will have 6 handshakes, 2nd will have 5, ....6th will have 1 and 7th will have 0   = 6+5+4+3+2+1= 
<gadget id="calculator">6+5+4+3+2+1</gadget>
<output>21</output>
21   if we generalize this: if there are n people then there will be n(n-1)/2 handshakes.   Ans.21)
<result>D</result>
If 7 persons meet at a reunion and each person shakes hands exactly once with each of the others, what is the total number of handshakes?