At the annual BrainBashers puzzle discussion conference, 20 people attended.
At the start of the conference, each person shook hands with every other person, how many handshakes took place in total?
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Hint
How many hands did the first person shake?
Answer
190.
The first person shook hands with 19 others, the second had already shook hands with the first and therefore shook 18 hands, etc: 19+18+17+16+15+14+13+12+11+10+9+8+7+6+5+4+3+2+1 = 190.
