Q32 of 64 Page 122

Everybody 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

Formula:- (i) nCr


Let total time of handshakes=nC2




⇒n2-n=132


⇒(n-12) (n+11)=0


n=12 or n=-11

More from this chapter

All 64 →
30

Total number of words formed by 2 vowels and 3 consonants taken from 4 vowels and 5 consonants is equal to

 31

A five digit number divisible by 3 is to be formed using the numbers 0, 1, 2, 3, 4 and 5 without repetitions. The total number of ways this can be done is

 33

The number of triangles that are formed by choosing the vertices from a set of 12 points, seven of which lie on the same line is

 34

The number of parallelograms that can be formed from a set of four parallel lines intersecting another set of three parallel lines is