In a get-together party, every person present shakes the hand of every other person. If there were 90 handshakes in all, how many persons were present at the party?
A. 15
B. 14
C. 16
D. 17
Answer:B
In a get-together party, every person present shakes the hand of every other person. If there were 90 handshakes in all, how many persons were present at the party?
A. 15
 B. 14
 C. 16
 D. 17

Explanation: Let the total number of persons present at the party be m, Then, [{x *(x−1)}/2] = 90.
