At a conference, 12 members shook hands with each 

other before & after the meeting. How many total 

number 

of hand shakes occurred?

• 100
• 132
• 145
• 144
• 121
Correct answer: 132
Explanation: The first person shook hands with 11 
remaining people, the second person also shook 
-hands with 11 people, but we count 10, as the hand 
shake with the first person has already been counted. 
Then add 9 for the third person, 8 for the fourth one & 
proceeding in this fashion we get: 11 + 10 + 9 + 8 + 7 + 
6 + 5 + 4 + 3 + 2 + 1 = 66. 

Hence 66 hand shakes took place before & 66 after the  
meeting, for a total of 132.