Question

Everybody in a room shakes hands with everybody else. The total number of handshakes is 45. The total number of persons in the room is

• A. 9
• B. 10
• C. 5
• D. 15

Answer 1

Answer: (B)

10

Answer 2

Number of handshakes = 45
$\Rightarrow \, {^nC_2} = 45$
$\Rightarrow \, n(n-1) = 90$
$\Rightarrow \, n = 10$