At a party, everyone shook hands with everybody else. There were 66 handshakes. How many people were at the party?

Topic: Data Science.

Difficulty: Easy.

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Objective: At a party, everyone shook hands with everybody else. There were 66 handshakes. How many people were at the party?

Short Answer: 12 people.

Full Solution

Since everyone shook hands with everybody else, let's assume there are n + 1 people.

Where n is the number of people

n * (n + 1)/2 = 66

n = 12

So there were 12 people at the party.