Question

Everybody in a room shakes hands with everybody else.the total number of handshakes is 66.Then the total number of persons in the room is :

Answer 1

only hints

Answer 2

for 2 ppl, handshakes = 1
for 3 people . handshakes = 1+2
for 4 people, handshakes = ?

Answer 3

1+2+3

Answer 4

@hartnn

Answer 5

12 person in meeting

Answer 6

I have reported you ^

Answer 7

so continuing that way, could u generalize it ?

Answer 8

for n ppl , 1+2+3+...n-1 = ?

Answer 9

Ok so how does this help

Answer 10

for n ppl, it will be n(n-1)/2 = 66
find n

Answer 11

So where did you get n(n-1)/2 from ?

Answer 12

1+2+3+4+.....n = sum of n numbers = n(n+1)/2
standard formula

Answer 13

Thanks Alot.

Answer 14

Here you have written n(n+1)/2 ?

Answer 15

yes, for n
for n-1 ?

Answer 16

just replace n by n-1

Answer 17

Ok so (n-1)(n+1)/2

Answer 18

no

Answer 19

suppose in a room n person are there.now two person make one hand shake.means total shake hand is C(n,2),but we are given total shake hand 66.solve C(n,2)=66 we have 12

Answer 20

(n-1)(n-1+1)/2

Answer 21

oh ok ok i got it now :) Thank you. let me find the answer.

Answer 22

n(n-1)/2=66

Answer 23

right

Answer 24

ya, solve that

Answer 25

12 right

Answer 26

So i got n^2-n-132=0

Answer 27

go on

Answer 28

ok i am trying

Answer 29

minus 12 and plus 11 solve this

Answer 30

n=-11 and n=12

Answer 31

number of pll can't be negative

Answer 32

-11 cannot be the answer

Answer 33

So 12 is the answer Thanks :)

Answer 34

welcome :)