Question

Every body in a room shakes hands with everybody else. The total number of hand shakes is 66. The total number of persons in the room is n 

(A) Last digit of n is 2 

(B) Sum of digit of n is 3 

(C) Product of digit of n is 2 

(D) n is prime number

Answer 1

Correct option (A) (B) (C)

Explanation:

Let total number of persons = n 

ⁿC₂ = 66 

⇒ n(n – 1) = 12.11 

⇒ n = 12