At the end of a conference, 10 people present all shake hands with each other once. How many handshakes will there be altogether?
Q1. At the end of a conference, 10 people present all shake hands with each other once. How many handshakes will there be altogether?
Answer: 45
Explanation: Each pair of 10 people shakes hands exactly once; total = C(10,2) = 10×9/2 = 45.