Question

At a party, everyone shook hands with everybody else. There were 66 handshakes. How many people were at the party?

Answer 1

math help!

Answer 2

@thisgirl9925 please message me!

Answer 3

Wouldn't you divide by 2? If there are 66 people, and two people have to shake hands... maybe 33, but not sure.

Answer 4

thanks for the help but im not sure thats it

Answer 5

@thisgirl9925 :/

Answer 6

It wouldn't be divided by 2 for sure

Answer 7

this questions hurts my head

Answer 8

Lets say that there's 4 people at a party, and we name them A, B, C, and D

Answer 9

All the possible hand shakes are AB, AC, AD, BC, BD, and CD

Answer 10

ok...

Answer 11

But we have to do that with 66 somehow

Answer 12

@SarahEZZMcK

Answer 13

Ok I got something

Answer 14

It looks like this is something called a triangular number sequence: http://www.mathsisfun.com/algebra/triangular-numbers.html

Answer 15

And we should be able to use this formula to solve: \[x _{n} = n(n+1)/2\]

Answer 16

ummm idek how to do that

Answer 17

12 people.
n=11 (when there are 12 people, there will be only 11 hand shake)
For checking it=n(n+1)/2=11*12/2=6*11=66 shakehands

Answer 18

thanks!

Answer 19

@thisgirl9925 unblock me pleasse!